postgresql: upgrade to fix fsync issue
According to https://www.postgresql.org/about/news/1920/
there was a long time serious problem how fsync works.
So postgresql should be upgraded on all Alpine releases which
are still maintained.
I tested upgrade on current stable and edge to version 11.2 and
it worked without issue (or I simply didn’t seen any till now)
(from redmine: issue id 10184, created on 2019-04-02, closed on 2019-04-03)