packaging: engine-backup: ignore also 'CREATE PROCEDURAL LANGUAGE'

When checking if a database is empty, ignore also 'CREATE PROCEDURAL
LANGUAGE', which is created by default in postgresl 8, in addition
to 'CREATE EXTENSION IF NOT EXISTS plpgsql' which is done in version 9.

Bug-Url: https://bugzilla.redhat.com/1066654
Bug-Url: https://bugzilla.redhat.com/1069131
Change-Id: Ib3772e27d0800792e97ae976f6c40484bd048fb6
Signed-off-by: Yedidyah Bar David <didi@redhat.com>