Fixed flaky MasterTest.LaunchDuplicateOfferTest.
Fixed flaky MasterTest.LaunchDuplicateOfferTest.

A couple of races could occur in the "launch tasks on multiple offers"
tests where recovered resources from purposely-failed invocations turned
into a subsequent resource offer and oversaturated the expect's.

Review: https://reviews.apache.org/r/25588

dforsyth/mesos,chhsia0/mesos,andschwa/mesos,chhsia0/mesos,chhsia0/mesos,Aman-Jain-14/customizedMesos,Gilbert88/mesos,asamerh4/mesos,verizonlabs/mesos,jpeach/mesos,kaysoky/mesos,neilconway/mesos,andschwa/mesos,kaysoky/mesos,asamerh4/mesos,andschwa/mesos,reneploetz/mesos,andschwa/mesos,craimbert/mesos,asamerh4/mesos,dforsyth/mesos,neilconway/mesos,reneploetz/mesos,craimbert/mesos,gsantovena/mesos,dforsyth/mesos,yuquanshan/customizedMesos,zmalik/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,abudnik/mesos,kaysoky/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,craimbert/mesos,craimbert/mesos,Gilbert88/mesos,dforsyth/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,yuquanshan/customizedMesos,gsantovena/mesos,chhsia0/mesos,Gilbert88/mesos,gsantovena/mesos,yuquanshan/customizedMesos,jpeach/mesos,andschwa/mesos,zmalik/mesos,reneploetz/mesos,verizonlabs/mesos,neilconway/mesos,kaysoky/mesos,asamerh4/mesos,neilconway/mesos,chhsia0/mesos,reneploetz/mesos,zmalik/mesos,zmalik/mesos,chhsia0/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,gsantovena/mesos,gsantovena/mesos,abudnik/mesos,abudnik/mesos,neilconway/mesos,Gilbert88/mesos,Aman-Jain-14/customizedMesos,zmalik/mesos,kaysoky/mesos,asamerh4/mesos,abudnik/mesos,verizonlabs/mesos,kaysoky/mesos,abudnik/mesos,jpeach/mesos,reneploetz/mesos,asamerh4/mesos,gsantovena/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,jpeach/mesos,abudnik/mesos,jpeach/mesos,andschwa/mesos,craimbert/mesos,craimbert/mesos,dforsyth/mesos,gsantovena/mesos,kaysoky/mesos,verizonlabs/mesos,abudnik/mesos,Gilbert88/mesos,Gilbert88/mesos,neilconway/mesos,andschwa/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,neilconway/mesos,reneploetz/mesos,jpeach/mesos,zmalik/mesos,craimbert/mesos,reneploetz/mesos,asamerh4/mesos,chhsia0/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,Gilbert88/mesos