Restrict move list based on offline node status
Restrict move list based on offline node status

This patch changes the Cluster.checkInstanceMove function to restrict
the target move list based on which nodes are online.
yiannist/ganeti,yiannist/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,bitemyapp/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,ganeti/ganeti,ganeti/ganeti,dimara/ganeti,leshchevds/ganeti,andir/ganeti,onponomarev/ganeti,grnet/snf-ganeti,andir/ganeti,andir/ganeti,leshchevds/ganeti,apyrgio/ganeti,grnet/snf-ganeti,mbakke/ganeti,mbakke/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,apyrgio/ganeti,apyrgio/snf-ganeti,leshchevds/ganeti,onponomarev/ganeti,bitemyapp/ganeti,dimara/ganeti