Switch from python-central to dh_python2.

Switch from python-central to dh_python2.

(This was initially done in the 4.0-0ubuntu12 upload but is now done slightly
 differently.)

Note that 2.6.6-6~ is needed (instead of 2.6.6-3~) because of
  "- create symlinks for files installed into /usr/share/pyshared/ if there
     are no other public modules available"

Closes: #606354
Signed-off-by: Didier Raboud <odyx@debian.org>