Support for checking the group of only the primary node
Support for checking the group of only the primary node

_CheckInstanceNodeGroups behaves in the old way with the default value
of the new parameter.

Signed-off-by: Adam Ingrassia <a033a528b603fed46f861d4b3542c417b99d41c8@google.com>
Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

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