Replaced slave's 'available' with 'allocated' in hierarchical allocator.
Replaced slave's 'available' with 'allocated' in hierarchical allocator.

Review: https://reviews.apache.org/r/35836

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