Revert "Add object-map to default RBD volume features"

This reverts commit 00e9cca6f0.

This causes RBD mapping to fail on Debian 10. Reverting but keeping in
history for future reference.

daemon-common/ceph.py

@@ -486,7 +486,7 @@ def add_volume(zk_conn, pool, name, size):
         size = '{}B'.format(size)
 
     # 2. Create the volume
-    retcode, stdout, stderr = common.run_os_command('rbd create --size {} --image-feature layering,exclusive-lock,object-map {}/{}'.format(size, pool, name))
+    retcode, stdout, stderr = common.run_os_command('rbd create --size {} --image-feature layering,exclusive-lock {}/{}'.format(size, pool, name))
     if retcode:
         return False, 'ERROR: Failed to create RBD volume "{}": {}'.format(name, stderr)