[Feature request] Specify what benchmarks to execute in task
[Feature request] Specify what benchmarks to execute in task

New feature:  ability to specify benchmark(s) executed as part of
rally task start command.

Change-Id: I39f07ed28bbba03c2073fa83364c72c419fd5644

amit0701/rally,cernops/rally,aplanas/rally,openstack/rally,pyKun/rally,gluke77/rally,openstack/rally,eonpatapon/rally,openstack/rally,redhat-openstack/rally,vganapath/rally,aforalee/RRally,shdowofdeath/rally,pyKun/rally,gluke77/rally,paboldin/rally,redhat-openstack/rally,vponomaryov/rally,amit0701/rally,afaheem88/rally,vganapath/rally,group-policy/rally,eayunstack/rally,paboldin/rally,eonpatapon/rally,aforalee/RRally,vefimova/rally,aplanas/rally,shdowofdeath/rally,eayunstack/rally,gluke77/rally,group-policy/rally,gluke77/rally,vganapath/rally,eayunstack/rally,vponomaryov/rally,go-bears/rally,afaheem88/rally,group-policy/rally,cernops/rally,openstack/rally,vefimova/rally,yeming233/rally,yeming233/rally,go-bears/rally,paboldin/rally,amit0701/rally,vganapath/rally