debian/control: record python3-packaging dependency for ceph-volume

debian/control: record python3-packaging dependency for ceph-volume

Commit 0985e201 added `from packaging import version` to
ceph_volume/util/encryption.py. On Debian and its derivatives, the
packaging module is provided by the python3-packaging package.

Add python3-packaging to ceph-volume's runtime dependencies to ensure
this import is satisfied.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Signed-off-by: Max R. Carrara <m.carrara@proxmox.com>
(cherry picked from commit a6ab6c63853d071f7383b0ce51d278de92fc3960)