Code cleanup in hierarchical_allocator_tests.cpp.
Code cleanup in hierarchical_allocator_tests.cpp.

This patch fixed the following issues in benchmark test:
1) Enabled templatized test fixture for DeclineOffers and
ResourceLabels.
2) Updated the output for the benchmark to be more clear.

Review: https://reviews.apache.org/r/49781/

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