Fix error msg for instances on offline nodes
Fix error msg for instances on offline nodes

Currently, for both primary and secondary offline nodes, we give the
same message:
- ERROR: instance instance14: instance lives on offline node(s) node3
- ERROR: instance instance15: instance lives on offline node(s) node3
- ERROR: instance instance16: instance lives on offline node(s) node3
- ERROR: instance instance17: instance lives on offline node(s) node3

This is confusing, as an offline primary is in a different category
than a secondary. The patch changes the warnings to have different
error messages:
- ERROR: instance instance14: instance has offline secondary node(s) node3
- ERROR: instance instance15: instance has offline secondary node(s) node3
- ERROR: instance instance16: instance lives on offline node node3
- ERROR: instance instance17: instance lives on offline node node3

Thanks to Alexander Schreiber <d79673dae93c3dc95c222708a03b3bbd3a746b44@google.com> for reporting this
issue.

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Alexander Schreiber <d79673dae93c3dc95c222708a03b3bbd3a746b44@google.com>

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