Make Hroller present master node last
Make Hroller present master node last

If in the list of nodes to be scheduled for maintaince,
one is marked as being the master node, schedule it
as the last node in the last group.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>

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