Fixed `balloon_framework_test.sh` and related test failures.
Fixed `balloon_framework_test.sh` and related test failures.

As executors no longer inherit environmental variables from the agent's
enviroment, `LD_LIBRARY_PATH` has to be set for the executor using the
`executor_environment_variables` flag. Otherwise the executor will fail
to run and as a consequence
`ContainerizerTest.ROOT_CGROUPS_BalloonFramework` also fails.

Review: https://reviews.apache.org/r/48954/

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