engine: upgrade postgres jdbc

- Upgrades PostgreSQL JDBC to version 9.1-901.jdbc4
- Removed postgresql.version from the pom, it was redundant with
  postgres.jdbc.version

Change-Id: I3bd31a6aae01e983f0ef995a57d5ab4884e9691b
Bug-Url: https://bugzilla.redhat.com/923260
Signed-off-by: Laszlo Hornyak <lhornyak@redhat.com>
(cherry picked from commit 743d03d75a6a1ac84b8a9df29c5d494b945de646)