Add PostgreSQL dir with socket to Docker container as a volume

Also explicitly set path to pg_dump 9.6 to avoid using old 9.5 postgres
client.

Fixes: PROD-31827

Change-Id: I727073c1caec40f11b87afcd64e31cdc50185a83
(cherry-picked from commit a1b31b7f2f39cfcd0ee2856a10a96f35d4c5e80c)
4 files changed