[COMMON] Fix postgres data persistence

[COMMON] Fix postgres data persistence

This changes fixes postgres data lost that occurs when postgres pods
are restarting.

When crunchy data postgres image starts, it runs /opt/cpm/bin/setenv.sh
script to set PGDATA folder. This script contains:

--
export PGDATA=/pgdata/$HOSTNAME

if [[ -v PGDATA_PATH_OVERRIDE ]]; then
  export PGDATA=/pgdata/$PGDATA_PATH_OVERRIDE
fi
--

Since postgres is now a deployment (commit 0b243b600), its pod name is
different on each startup, hence HOSTNAME and PGDATA are also
different each time.

This change is leveraging crunchy data PGDATA_PATH_OVERRIDE environment
variable to set PGDATA to a fixed path. By default, this path is set to
/pgdata/data.

Issue-ID: CPS-271
Change-Id: Icc0f05d64230a98bc21d8f2a74c12c6661e05482
Signed-off-by: Bruno Sakoto <bruno.sakoto@bell.ca>