Start ping listener also for postgresql

We can make use of the automatic connection disposal
for PostgreSQL as well.

Closes-Bug: #1298310
Change-Id: Ifb498b64f6a4305c6639afaeed246394043decd1
(cherry picked from commit 4a591eaafe035fa3fd508c910f057bfa8ff51005)
Merge "Start ping listener also for postgresql" into stable/icehouse