Add support for ceph-proxy dataset

Add parsing of munged data presented by the ceph-proxy
charm in the ceph-public-address relation key; this
includes dropping the addition of the port to the values
added to the list of monitor hosts - this is not required
and the ceph-proxy may provide that data as part of the
ceph-public-address.

This change brings this interface inline with existing
ceph context support in the openstack charm helpers.

Change-Id: Id4d7b5df711c378763d5adb54269a3ede344dd45

.gitreview

@@ -0,0 +1,4 @@
+[gerrit]
+host=review.openstack.org
+port=29418
+project=openstack/charm-interface-ceph-client.git

requires.py

@@ -113,7 +113,12 @@ class CephClientRequires(RelationBase):
         """List of all monitor host public addresses"""
         hosts = []
         addrs = self.get_remote_all('ceph-public-address')
-        for addr in addrs:
-            hosts.append('{}:6789'.format(format_ipv6_addr(addr) or addr))
+        for ceph_addrs in addrs:
+            # NOTE(jamespage): This looks odd but deals with
+            #                  use with ceph-proxy which
+            #                  presents all monitors in
+            #                  a single space delimited field.
+            for addr in ceph_addrs.split(' '):
+                hosts.append(format_ipv6_addr(addr) or addr)
         hosts.sort()
         return hosts