The ceph version supported by kolla is now luminous, but the latest
ceph version of ubuntu's apt source is mimic, so there will be
problems with ceph deployment.
This patch solves this problem by specifying the version of the ceph
package installed.
Change-Id: Ibea3498589b6c3c1512e558919c6ea00c95686cb
Closes-bug: #1793667
78001f06a7