Add new CLI options for min gain during balancing
Add new CLI options for min gain during balancing

Recent hbal seems to run many steps for small improvements (< 1e-3), so
we should stop early in this case.

We add a new option (-g), that will be used for the minimum gain during
balancing. This check will only become active when the cluster score is
below a threshold (--min-gain-limit), so as to not stop rebalances too
early.

andir/ganeti,ganeti-github-testing/ganeti-test-1,grnet/snf-ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,ganeti/ganeti,leshchevds/ganeti,onponomarev/ganeti,bitemyapp/ganeti,andir/ganeti,leshchevds/ganeti,bitemyapp/ganeti,ganeti/ganeti,ganeti/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,yiannist/ganeti,apyrgio/ganeti,dimara/ganeti,apyrgio/snf-ganeti,andir/ganeti,grnet/snf-ganeti,mbakke/ganeti,yiannist/ganeti,onponomarev/ganeti,apyrgio/ganeti,mbakke/ganeti,leshchevds/ganeti,dimara/ganeti