recipe/postgres: support non standard port

even though the recipe has a required option for port, it was not used
and server was always listening on default (5432) port
4 jobs for fix/postgres_recipe_test in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Jerome.Python2

00:17:16

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:14:23

passed SlapOS.Eggs.UnitTest-Jerome.Python2

00:52:13

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:48:19