Add --first-job-group to hbal
Add --first-job-group to hbal

...to support iterative utilization-based cluster
balancing, allowing for reevaluation of the load
after each group of moves.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>

onponomarev/ganeti,yiannist/ganeti,andir/ganeti,mbakke/ganeti,yiannist/ganeti,andir/ganeti,dimara/ganeti,grnet/snf-ganeti,dimara/ganeti,leshchevds/ganeti,bitemyapp/ganeti,onponomarev/ganeti,ganeti/ganeti,bitemyapp/ganeti,leshchevds/ganeti,grnet/snf-ganeti,yiannist/ganeti,andir/ganeti,mbakke/ganeti,ganeti/ganeti,leshchevds/ganeti,ganeti/ganeti,mbakke/ganeti