Used posix launcher for multiple slave tests.
Used posix launcher for multiple slave tests.

Linux launcher does not work when there are multiple slaves running on
a single host because it uses cgroups which is global.

Review: https://reviews.apache.org/r/52445

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