cephadm: fix host-maintenance command always exiting with a failure

cephadm: fix host-maintenance command always exiting with a failure

The host-maintenance command would always fail because
command_maintenance always returns a string. This string is passed to
sys.exit and thus always gets printed and causes a non-zero exit code.
Fix the command line behavior by renaming the original function and
adding a new command_maintenance that prints the string and returns an
int like other command_* functions do.

Fixes: https://tracker.ceph.com/issues/65122
Signed-off-by: John Mulligan <jmulligan@redhat.com>
(cherry picked from commit 0a137b140e47d02b03d133adb55e62aa0de7b984)

Conflicts:
	src/cephadm/cephadm.py
	src/cephadm/tests/test_cephadm.py