Introduced 'roles' validation in master.
Introduced 'roles' validation in master.

Leveraged `validation::framework::validate()` function introduced
in a previous patch to validate FrameworkInfo when a framework
subscribes with the master.

Review: https://reviews.apache.org/r/54301/

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