Rename lib/ceph to lib/charms_ceph

The new python3-ceph-common deb package (introduced in ceph octopus)
adds a new ceph directory (a parent package in python terms) in
/usr/lib/python3/dist-packages/ceph/. This results in a conflict with
charm-ceph-osd/lib/ceph/. For example, with the current import of
ceph.utils in hooks/hooks.py, Python finds no utils.py in
/usr/lib/python3/dist-packages/ceph/ and then stops searching.
Therefore, rename lib/ceph to lib/charms_ceph to avoid the conflict.

Depends-On: https://review.opendev.org/#/c/709226
Change-Id: I433537805ae56dc7a42e9d34ea6d491ffb4c79c0

hooks/hooks.py

@@ -23,7 +23,7 @@ import uuid
 sys.path.append('lib')
 
 import ceph_rgw as ceph
-import ceph.utils as ceph_utils
+import charms_ceph.utils as ceph_utils
 import multisite
 
 from charmhelpers.core.hookenv import (

lib/charms_ceph/broker.py

@@ -18,11 +18,11 @@ import os
 
 from tempfile import NamedTemporaryFile
 
-from ceph.utils import (
+from charms_ceph.utils import (
     get_cephfs,
     get_osd_weight
 )
-from ceph.crush_utils import Crushmap
+from charms_ceph.crush_utils import Crushmap
 
 from charmhelpers.core.hookenv import (
     log,