debian: make ceph depend on ceph-common >= 0.67

The older versions of ceph-common (ceph CLI, in particular) can't talk to 
newer clusters.  The primary change happened with dumpling when the new CLI
and rest-api changes were made.  Although in reality ceph doesn't care what
version of ceph-common is installed, in practice this forces ceph-common to
get upgraded along with ceph and avoids some user pain.

Fixes: #7641 Signed-off-by: Sage Weil <sage@inktank.com>