mgr/dashboard: Fix 500 error while exiting out of maintenance

mgr/dashboard: Fix 500 error while exiting out of maintenance

When you add a host in maintenance mode and then exit the maintenance
mode, a 500 server error will popup which will interrupt the whole
exit maintenance process and leave the host in an unknown/offline state.
It happened when I was setting the status of the host through the
HostSpec(). With this change, I am using the enter_maintenance api of
the orch to enable the maintenance.

Fixes: https://tracker.ceph.com/issues/51218
Signed-off-by: Nizamudeen A <nia@redhat.com>
(cherry picked from commit ea89b60e3f5e73a653eebf5cdcc3227acb7b2e62)

Conflicts:
   	 src/pybind/mgr/dashboard/controllers/host.py
 - Removed the addr and label variables since its not backported yet to
   pacific
 - Removed Versioning since for pacific this endpoint is not yet
   versioned to 0.1
	src/pybind/mgr/dashboard/services/orchestrator.py
 - Removed the addr and label variables since its not backported yet to
   pacific
	src/pybind/mgr/dashboard/frontend/src/app/shared/api/host.service.ts
 - Didn't included this file because the changes in there are irrelevant
   in pacific
	src/pybind/mgr/dashboard/openapi.yaml
 - Regenerated the openapi file