integration helpers: Fix concurrent calls to start_docker().
integration helpers: Fix concurrent calls to start_docker().

Signed-off-by: Andrea Luzzardi <442ffe3ffbfd024afcf0b7f8b108d05bca3aae43@gmail.com>

gdevillele/docker.github.io,doronp/swarm,pssahi/swarm,joaofnfernandes/docker.github.io,alexisbellido/docker.github.io,kyhavlov/swarm,thaJeztah/docker.github.io,barais/swarm,denverdino/denverdino.github.io,alexisbellido/docker.github.io,snrism/swarm,raoofm/swarm,londoncalling/docker.github.io,FollowMyDev/swarm,zkcrescent/swarm,shubheksha/docker.github.io,shin-/docker.github.io,denverdino/swarm-1,shin-/docker.github.io,BSWANG/denverdino.github.io,joaofnfernandes/docker.github.io,LuisBosquez/docker.github.io,denverdino/docker.github.io,BSWANG/denverdino.github.io,abronan/swarm,jeffjen/swarm,xFragger/swarm,gradywang/swarm,denverdino/docker.github.io,phiroict/docker,ealang/swarm,Aorjoa/swarm,u2mejc/swarm,troy0820/docker.github.io,auzias/swarm,aidora/pisces,fugr/swarm,shin-/docker.github.io,bdwill/docker.github.io,rillig/docker.github.io,joeuo/docker.github.io,aduermael/docker.github.io,sfsmithcha/swarm,jay-lau/swarm,tangkun75/swarm,linecheng/swarm,anweiss/docker.github.io,denverdino/denverdino.github.io,gdevillele/docker.github.io,anweiss/docker.github.io,ricca742/swarm,mgoelzer/swarm,christophelec/swarm,therealbill/swarm,morpheyesh/swarm,rillig/docker.github.io,zkcrescent/swarm,bpradipt/swarm,LukasBacigal/swarm,EderRoger/swarm,anweiss/docker.github.io,rav121/swarm,jimmyxian/swarm,adouang/swarm,rutulpatel/swarm,sanscontext/docker.github.io,mrjana/swarm,shahankhatch/swarm,shot/swarm,krystism/swarm,danix800/docker.github.io,srikalyan/swarm,jzwlqx/denverdino.github.io,CodeNow/swarm,akerbis/armhf-swarm,gonkulator/swarm,morpheyesh/swarm,rajdeepd/swarm,johnstep/docker.github.io,everett-toews/swarm,bdwill/docker.github.io,ezrasilvera/swarm,FreedomWangLi/swarm,joeuo/docker.github.io,jimmycmh/swarm,johnstep/docker.github.io,jeffjen/swarm,ehazlett/swarm,bsmr-docker/swarm,shubheksha/docker.github.io,resouer/swarm,liubin/swarm,rajdeepd/swarm,troy0820/docker.github.io,denverdino/swarm,tangkun75/swarm,fugr/swarm,MHBauer/swarm,jdamick/swarm,errordeveloper/swarm,CodeNow/swarm,polyverse-security/swarm,anweiss/docker.github.io,jimenez/swarm,allencloud/swarm,marsmensch/swarm,auzias/swarm,parapsyche/swarm,megamsys/swarm,shubheksha/docker.github.io,alexisbellido/docker.github.io,JimGalasyn/docker.github.io,denverdino/swarm-1,cgvarela/swarm,joaofnfernandes/docker.github.io,denverdino/denverdino.github.io,sanscontext/docker.github.io,londoncalling/docker.github.io,menglingwei/denverdino.github.io,ejholmes/swarm,LuisBosquez/docker.github.io,CiaranCostello/swarm,BSWANG/denverdino.github.io,PeoplePerHour/libswarm,gdevillele/docker.github.io,shahankhatch/swarm,aduermael/docker.github.io,docker/docker.github.io,akerbis/armhf-swarm,shubheksha/docker.github.io,johnstep/docker.github.io,Spritekin/swarm,schmunk42/swarm,docker-zh/docker.github.io,londoncalling/docker.github.io,aidora/pisces,FollowMyDev/swarm,affo/swarm,LukasBacigal/swarm,jzwlqx/denverdino.github.io,jzwlqx/denverdino.github.io,swarm-hooks/swarm,jimmyxian/swarm,jimmycmh/swarm,LuisBosquez/docker.github.io,menglingwei/denverdino.github.io,rillig/docker.github.io,unodba/swarm,phiroict/docker,bpradipt/swarm,ezrasilvera/SwarmACLs,francisbouvier/swarm,ch3lo/swarm,mgoelzer/swarm,abronan/swarm,allencloud/swarm,sanscontext/docker.github.io,dims/swarm,thaJeztah/docker.github.io,yp-engineering/swarm,NunoEdgarGub1/swarm,sanscontext/docker.github.io,bdwill/docker.github.io,rutulpatel/swarm,gdevillele/docker.github.io,bsmr-docker/swarm,errordeveloper/swarm,francisbouvier/swarm,qianzhangxa/swarm,iaintshine/swarm,BSWANG/denverdino.github.io,menglingwei/denverdino.github.io,doronp/swarm,riuvshin/swarm,barais/swarm,everett-toews/swarm,mavenugo/swarm,danix800/docker.github.io,vlajos/swarm,denverdino/docker.github.io,gonkulator/swarm,echupriyanov/swarm,NunoEdgarGub1/swarm,docker/docker.github.io,alexisbellido/docker.github.io,Aorjoa/swarm,aduermael/docker.github.io,ezrasilvera/SwarmACLs,phiroict/docker,bdwill/docker.github.io,EderRoger/swarm,iaintshine/swarm,ehazlett/swarm,polyverse-security/swarm,danix800/docker.github.io,phiroict/docker,xFragger/swarm,phiroict/docker,mrjana/swarm,cgvarela/swarm,therealbill/swarm,denverdino/swarm,docker/docker.github.io,pdevine/swarm,BSWANG/swarm,mavenugo/swarm,shubheksha/docker.github.io,jdamick/swarm,joeuo/docker.github.io,docker/docker.github.io,rchicoli/swarm,shot/swarm,Spritekin/swarm,BSWANG/swarm,denverdino/denverdino.github.io,swarm-hooks/swarm,ezrasilvera/swarm,dnephin/swarm,christophelec/swarm,troy0820/docker.github.io,affo/swarm,rancher/swarm,LuisBosquez/docker.github.io,rchicoli/swarm,thaJeztah/docker.github.io,docker-zh/docker.github.io,deis/swarm,denverdino/docker.github.io,jzwlqx/denverdino.github.io,moxiegirl/swarm,vlajos/swarm,dnephin/swarm,alexisbellido/docker.github.io,u2mejc/swarm,FreedomWangLi/swarm,jimenez/swarm,aduermael/docker.github.io,megamsys/swarm,jzwlqx/denverdino.github.io,shin-/docker.github.io,docker-zh/docker.github.io,docker-zh/docker.github.io,parapsyche/swarm,ejholmes/swarm,CiaranCostello/swarm,tranceitionalMynd/swarm,rillig/docke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