balance function: use the movable flag directly
balance function: use the movable flag directly

Instead of deciding based on secondary node, use the new flag.

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