debian pkg: record python3-packaging dependency for ceph-volume

debian pkg: record python3-packaging dependency for ceph-volume

Since commit 0985e201342 ("ceph-volume: use 'no workqueue' options
with dmcrypt") the python "packaging" module is used to parse the
cryptsetup version output, but the debian packaging was not updated to
record that new dependency.

So simply record this in the d/control file, adding a <pkg>.requires
file seemed to not really winning us anything here.

Fixes: https://tracker.ceph.com/issues/67290
Fixes: 0985e201342fa53c014a811156aed661b4b8f994
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>