dockerfile: use the `PG_HOME` macro where ever possible
dockerfile: use the `PG_HOME` macro where ever possible

crobays/docker-postgresql,sameersbn/docker-postgresql,arkkanoid/docker-postgresql,zires/docker-postgresql,timclassic/docker-postgresql,bokysan/docker-postgresql,logandg/docker-postgis,markrowsoft/docker-postgres-bdr,mental-docker/postgresql,whatever4711/rpi-postgresql,boky8/docker-postgresql