Remove package require for cinder-volume

Package 'cinder-volume' is only defined in Debian distros. Leaving it defined
breaks RedHat distros.

Since $::cinder::params::ceph_init_override isn't provided by either package,
we can remove the require and just rely on the notify to do the required work.

Change-Id: I51c2a274d0fd6b00f2c4ea7e52e15066c3fd83fc