Fix python3 compatibility of rbd get_fsid

In python3 conn.get_fsid() is represented as binary.
Because of this, direct_url is corrupted in DB.
This patch is fixing this. More informations in
closing bug.

Closes-Bug: #1816721

Change-Id: I6a89042fae63bf5c9096a6bee6774aebf3f5864b
(cherry picked from commit 9c73370358)

glance_store/_drivers/rbd.py

@@ -24,6 +24,7 @@ import logging
 import math
 
 from oslo_config import cfg
+from oslo_utils import encodeutils
 from oslo_utils import units
 from six.moves import urllib
 
@@ -469,7 +470,18 @@ class Store(driver.Store):
                                  rados_id=self.user) as conn:
             fsid = None
             if hasattr(conn, 'get_fsid'):
-                fsid = conn.get_fsid()
+                # Librados's get_fsid is represented as binary
+                # in py3 instead of str as it is in py2.
+                # This is causing problems with ceph.
+                # Decode binary to str fixes these issues.
+                # Fix with encodeutils.safe_decode CAN BE REMOVED
+                # after librados's fix will be stable.
+                #
+                # More informations:
+                # https://bugs.launchpad.net/glance-store/+bug/1816721
+                # https://bugs.launchpad.net/cinder/+bug/1816468
+                # https://tracker.ceph.com/issues/38381
+                fsid = encodeutils.safe_decode(conn.get_fsid())
             with conn.open_ioctx(self.pool) as ioctx:
                 order = int(math.log(self.WRITE_CHUNKSIZE, 2))
                 LOG.debug('creating image %s with order %d and size %d',