Fix race condition in test_server_io
Fix race condition in test_server_io

In test_server_io:gc/1 we collect the group leaders for all processes.
We must handle the case that a process has died after processes/0
was called and process_info(P, group_leader) is called.

RoadRunnr/otp,schlagert/otp,hairyhum/otp,aboroska/otp,jamesruan/otp,RichMorin/otp,saleyn/otp,vinoski/otp,emile/otp,mujiatong/otp,dumbbell/otp,paulcager/otp,emacsmirror/erlang,Teino1978-Corp/erlang-otp,jinshana/otp,schlagert/otp,yangchengjian/otp,electricimp/otp,saleyn/otp,cobusc/otp,jemsbhai/otp,NOMORECOFFEE/otp,c-rack/otp,sammoth-wazoku/otp,weisslj/otp,weisslj/otp,ahmedshafeeq/otp,kvakvs/otp,goertzenator/otp,tuncer/otp,lemenkov/otp,lucafavatella/otp,derek121/otp,riverrun/otp,matwey/otp,klarna/otp,rlipscombe/otp,vinoski/otp,potatosalad/otp,g-andrade/otp,lhslll/otp,falkevik/otp,lhslll/otp,kvakvs/otp,vic/otp,rlipscombe/otp,fenollp/otp,awetzel/otp,lianghaivv/otp,cobusc/otp,RJ/otp,emacsmirror/erlang,awetzel/otp,sammoth-wazoku/otp,kvakvs/otp,RichMorin/otp,lrascao/otp,yangchengjian/otp,lantti/otp,RGafiyatullin/otp,bernardd/otp,lhslll/otp,lrascao/otp,lucafavatella/otp,entropiae/otp,isvilen/otp,massemanet/otp,cobusc/otp,goertzenator/otp,palas/otp,RJ/otp,vic/otp,lightcyphers/otp,dgud/otp,haguenau/otp,vladdu/otp,RaimoNiskanen/otp,potatosalad/otp,Teino1978-Corp/otp,bugs-erlang-org/otp,uabboli/otp,jemsbhai/otp,palas/otp,Teino1978-Corp/otp,Teino1978-Corp/erlang-otp,vinoski/otp,RJ/otp,g-andrade/otp,emacsmirror/erlang,cnbin/otp,legoscia/otp,mikpe/otp,ferd/otp,ader1990/otp,vinoski/otp,palas/otp,cnbin/otp,derek121/otp,matwey/otp,gjaldon/otp,entropiae/otp,g-andrade/otp,paladim/otp,bugs-erlang-org/otp,RichMorin/otp,lantti/otp,sitexa/otp,cnbin/otp,falkevik/otp,lucafavatella/otp,goertzenator/otp,basho/otp,RoadRunnr/otp,dgud/otp,bjorng/otp,jinshana/otp,sdebnath/otp,potatosalad/otp,weisslj/otp,jinshana/otp,mikpe/otp,ader1990/otp,legoscia/otp,johanclaesson/otp,marquisthunder/otp,RJ/otp,RGafiyatullin/otp,psyeugenic/otp,emacsmirror/erlang,NOMORECOFFEE/otp,RichMorin/otp,entropiae/otp,sammoth-wazoku/otp,NOMORECOFFEE/otp,vladdu/otp,RGafiyatullin/otp,lrascao/otp,msantos/otp,yangchengjian/otp,jamesruan/otp,jamesruan/otp,basho/otp,platinumthinker/otp,mikpe/otp,jj1bdx/otp,dumbbell/otp,massemanet/otp,yangchengjian/otp,bugs-erlang-org/otp,c-rack/otp,emacsmirror/erlang,msantos/otp,stolen/otp,paladim/otp,isvilen/otp,cnbin/otp,theom/otp,hairyhum/otp,sammoth-wazoku/otp,vic/otp,ader1990/otp,bernardd/otp,lucafavatella/otp,release-project/otp,stolen/otp,Teino1978-Corp/erlang-otp,awetzel/otp,goertzenator/otp,jj1bdx/otp,paulcager/otp,massemanet/otp,sdebnath/otp,vladdu/otp,dgud/otp,gjaldon/otp,goertzenator/otp,ader1990/otp,bsmr-erlang/otp,Teino1978-Corp/erlang-otp,sdebnath/otp,krishnakumar4a4/otp,derek121/otp,sammoth-wazoku/otp,vinoski/otp,entropiae/otp,jj1bdx/otp,NOMORECOFFEE/otp,bernardd/otp,beni55/otp,potatosalad/otp,sammoth-wazoku/otp,saleyn/otp,krishnakumar4a4/otp,fenollp/otp,release-project/otp,vic/otp,potatosalad/otp,neeraj9/otp,msantos/otp,johanclaesson/otp,lucafavatella/otp,isvilen/otp,bugs-erlang-org/otp,neeraj9/otp,RaimoNiskanen/otp,g-andrade/otp,benoitc/otp-1,mikpe/otp,krishnakumar4a4/otp,aboroska/otp,Teino1978-Corp/erlang-otp,theom/otp,johanclaesson/otp,msantos/otp,sdebnath/otp,bsmr-erlang/otp,ahmedshafeeq/otp,lemenkov/otp,erlang/otp,Teino1978-Corp/otp,fenollp/otp,bjorng/otp,uabboli/otp,awetzel/otp,bsmr-erlang/otp,platinumthinker/otp,falkevik/otp,theom/otp,weisslj/otp,sitexa/otp,lightcyphers/otp,vinoski/otp,emile/otp,bugs-erlang-org/otp,erlang/otp,paladim/otp,cobusc/otp,marquisthunder/otp,uabboli/otp,fenollp/otp,paladim/otp,bugs-erlang-org/otp,vladdu/otp,dgud/otp,riverrun/otp,release-project/otp,benoitc/otp-1,paladim/otp,hairyhum/otp,yangchengjian/otp,sitexa/otp,haguenau/otp,riverrun/otp,legoscia/otp,kvakvs/otp,neeraj9/otp,beni55/otp,entropiae/otp,mujiatong/otp,sitexa/otp,lhslll/otp,haguenau/otp,Teino1978-Corp/otp,getong/otp,uabboli/otp,isvilen/otp,fenollp/otp,hairyhum/otp,legoscia/otp,aboroska/otp,emacsmirror/erlang,c-rack/otp,lrascao/otp,g-andrade/otp,Teino1978-Corp/otp,lucafavatella/otp,bernardd/otp,theom/otp,lianghaivv/otp,bjorng/otp,getong/otp,jemsbhai/otp,entropiae/otp,entropiae/otp,rlipscombe/otp,sitexa/otp,sitexa/otp,paulcager/otp,platinumthinker/otp,massemanet/otp,release-project/otp,dgud/otp,vic/otp,mujiatong/otp,RoadRunnr/otp,getong/otp,rlipscombe/otp,lianghaivv/otp,hairyhum/otp,bsmr-erlang/otp,getong/otp,platinumthinker/otp,basho/otp,dgud/otp,stolen/otp,Teino1978-Corp/erlang-otp,RaimoNiskanen/otp,rlipscombe/otp,jemsbhai/otp,matwey/otp,sdebnath/otp,benoitc/otp-1,jj1bdx/otp,uabboli/otp,ahmedshafeeq/otp,weisslj/otp,stolen/otp,jj1bdx/otp,sdebnath/otp,lhslll/otp,RaimoNiskanen/otp,vic/otp,rlipscombe/otp,johanclaesson/otp,awetzel/otp,RoadRunnr/otp,electricimp/otp,theom/otp,aboroska/otp,legoscia/otp,neeraj9/otp,lightcyphers/otp,kvakvs/otp,massemanet/otp,gjaldon/otp,mikpe/otp,bsmr-erlang/otp,VincentHHL/otp,jj1bdx/otp,goertzenator/otp,Teino1978-Corp/erlang-otp,g-andrade/otp,GinjaNinja32/otp,ahmedshafeeq/otp,lemenkov/otp,massemanet/otp,GinjaNinja32/otp,lrascao/otp,aboroska/otp,cnbin/otp,electricimp/otp,tuncer/otp,falkevik/otp,cobusc/otp,gjaldon/otp,mujiatong/otp,VincentHHL/otp,release-project/otp,yangchengjian/otp,derek121/otp,dumbbell/otp,falkevik/otp,GinjaNinja32/otp,ader1990/otp,GinjaNinja32/otp,lhslll/otp,vinoski/otp,isvilen/otp,erlang/otp,basho/otp,sdebnath/otp,aboroska/otp,platinumthinker/otp,stolen/otp,isvilen/otp,paulcager/otp,krishnakumar4a4/otp,RoadRunnr/otp,jemsbhai/otp,bjorng/otp,RoadRunnr/otp,emile/otp,krishnakumar4a4/otp,sitexa/otp,aboroska/otp,schlagert/otp,potatosalad/otp,VincentHHL/otp,sammoth-wazoku/otp,legoscia/otp,jamesruan/otp,derek121/otp,palas/otp,bugs-erlang-org/otp,jamesruan/otp,RoadRunnr/otp,lhslll/otp,beni55/otp,saleyn/otp,mujiatong/otp,riverrun/otp,jj1bdx/otp,matwey/otp,massemanet/otp,paladim/otp,jinshana/otp,mikpe/otp,uabboli/otp,lemenkov/otp,lucafavatella/otp,NOMORECOFFEE/otp,mujiatong/otp,falkevik/otp,tuncer/otp,neeraj9/otp,weisslj/otp,bjorng/otp,derek121/otp,krishnakumar4a4/otp,psyeugenic/otp,haguenau/otp,benoitc/otp-1,rlipscombe/otp,potatosalad/otp,RJ/otp,matwey/otp,platinumthinker/otp,klarna/otp,sammoth-wazoku/otp,massemanet/otp,enikki/otp,saleyn/otp,g-andrade/otp,mikpe/otp,benoitc/otp-1,lrascao/otp,emacsmirror/erlang,enikki/otp,falkevik/otp,jj1bdx/otp,psyeugenic/otp,psyeugenic/otp,bernardd/otp,release-project/otp,beni55/otp,electricimp/otp,electricimp/otp,fenollp/otp,basho/otp,RGafiyatullin/otp,bernardd/otp,RichMorin/otp,cnbin/otp,RGafiyatullin/otp,enikki/otp,weisslj/otp,klarna/otp,bernardd/otp,vinoski/otp,ader1990/otp,bsmr-erlang/otp,jinshana/otp,ferd/otp,getong/otp,sitexa/otp,c-rack/otp,bugs-erlang-org/otp,lucafavatella/otp,ferd/otp,paulcager/otp,vladdu/otp,ader1990/otp,kvakvs/otp,ferd/otp,isvilen/otp,erlang/otp,fenollp/otp,emacsmirror/erlang,Teino1978-Corp/otp,potatosalad/otp,ahmedshafeeq/otp,marquisthunder/otp,basho/otp,yangchengjian/otp,NOMORECOFFEE/otp,hairyhum/otp,RaimoNiskanen/otp,VincentHHL/otp,matwey/otp,saleyn/otp,mikpe/otp,getong/otp,kvakvs/otp,RichMorin/otp,mikpe/otp,dumbbell/otp,Teino1978-Corp/erlang-otp,bsmr-erlang/otp,ader1990/otp,RJ/otp,mikpe/otp,GinjaNinja32/otp,mujiatong/otp,c-rack/otp,basho/otp,mujiatong/otp,ferd/otp,jj1bdx/otp,tuncer/otp,paladim/otp,erlang/otp,riverrun/otp,marquisthunder/otp,riverrun/otp,bernardd/otp,dumbbell/otp,weisslj/otp,palas/otp,potatosalad/otp,emile/otp,falkevik/otp,klarna/otp,lemenkov/otp,lianghaivv/otp,lantti/otp,massemanet/otp,benoitc/otp-1,electricimp/otp,beni55/otp,lhslll/otp,lantti/otp,derek121/otp,krishnakumar4a4/otp,jj1bdx/otp,isvilen/otp,ferd/otp,jinshana/otp,psyeugenic/otp,neeraj9/otp,emile/otp,msantos/otp,awetzel/otp,getong/otp,RichMorin/otp,paulcager/otp,c-rack/otp,bjorng/otp,g-andrade/otp,schlagert/otp,bjorng/otp,basho/otp,goertzenator/otp,RGafiyatullin/otp,sdebnath/otp,GinjaNinja32/otp,VincentHHL/otp,RoadRunnr/otp,jinshana/otp,schlagert/otp,g-andrade/otp,lantti/otp,erlang/otp,psyeugenic/otp,cobusc/otp,awetzel/otp,bjorng/otp,schlagert/otp,jamesruan/otp,palas/otp,legoscia/otp,RichMorin/otp,vic/otp,ahmedshafeeq/otp,marquisthunder/otp,marquisthunder/otp,cnbin/otp,cnbin/otp,electricimp/otp,vladdu/otp,dumbbell/otp,theom/otp,kvakvs/otp,theom/otp,bsmr-erlang/otp,enikki/otp,RaimoNiskanen/otp,lightcyphers/otp,aboroska/otp,c-rack/otp,vinoski/otp,dumbbell/otp,schlagert/otp,g-andrade/otp,ferd/otp,klarna/otp,paulcager/otp,jemsbhai/otp,jinshana/otp,saleyn/otp,release-project/otp,krishnakumar4a4/otp,uabboli/otp,platinumthinker/otp,jamesruan/otp,haguenau/otp,neeraj9/otp,dgud/otp,NOMORECOFFEE/otp,emile/otp,dumbbell/otp,dgud/otp,dgud/otp,legoscia/otp,goertzenator/otp,lrascao/otp,tuncer/otp,fenollp/otp,ahmedshafeeq/otp,NOMORECOFFEE/otp,palas/otp,neeraj9/otp,lemenkov/otp,erlang/otp,matwey/otp,psyeugenic/otp,marquisthunder/otp,electricimp/otp,tuncer/otp,VincentHHL/otp,basho/otp,emile/otp,bjorng/otp,paulcager/otp,haguenau/otp,tuncer/otp,c-rack/otp,jemsbhai/otp,benoitc/otp-1,lantti/otp,lianghaivv/otp,release-project/otp,lightcyphers/otp,johanclaesson/otp,enikki/otp,isvilen/otp,falkevik/otp,ahmedshafeeq/otp,cobusc/otp,klarna/otp,lrascao/otp,rlipscombe/otp,hairyhum/otp,riverrun/otp,bsmr-erlang/otp,kvakvs/otp,dgud/otp,gjaldon/otp,enikki/otp,jamesruan/otp,klarna/otp,beni55/otp,lemenkov/otp,klarna/otp,RGafiyatullin/otp,gjaldon/otp,jemsbhai/otp,getong/otp,psyeugenic/otp,johanclaesson/otp,derek121/otp,vic/otp,legoscia/otp,entropiae/otp,johanclaesson/otp,RJ/otp,stolen/otp,haguenau/otp,hairyhum/otp,lianghaivv/otp,uabboli/otp,lemenkov/otp,lightcyphers/otp,gjaldon/otp,gjaldon/otp,haguenau/otp,lianghaivv/otp,GinjaNinja32/otp,paladim/otp,release-project/otp,ferd/otp,saleyn/otp,dumbbell/otp,rlipscombe/otp,lianghaivv/otp,yangchengjian/otp,bernardd/otp,stolen/otp,goertzenator/otp,Teino1978-Corp/otp,erlang/otp,vinoski/otp,vladdu/otp,erlang/otp,GinjaNinja32/otp,marquisthunder/otp,stolen/otp,cobusc/otp,RJ/otp,theom/otp,erlang/otp,awetzel/otp,emile/otp,lightcyphers/otp,beni55/otp,tuncer/otp,vladdu/otp,dumbbell/otp,rlipscombe/otp,lrascao/otp,platinumthinker/otp,vladdu/otp,riverrun/otp,potatosalad/otp,bjorng/otp,Teino1978-Corp/otp,getong/otp,RaimoNiskanen/otp,RaimoNiskanen/otp,palas/otp,VincentHHL/otp,lightcyphers/otp,msantos/otp,benoitc/otp-1,enikki/otp,getong/otp,tuncer/otp,emacsmirror/erlang,msantos/otp,RGafiyatullin/otp,ferd/otp,isvilen/otp,schlagert/otp,fenollp/otp,uabboli/otp,aboroska/otp,lantti/otp,VincentHHL/otp,electricimp/otp,enikki/otp,saleyn/otp,RoadRunnr/otp,emile/otp,johanclaesson/otp,ahmedshafeeq/otp,matwey/otp,RaimoNiskanen/otp,beni55/otp,msantos/otp,weisslj/otp,lantti/otp,emacsmirror/erlang,matwey/otp