Empty postgres.pid file is still existing in gear after stop

https://bugzilla.redhat.com/show_bug.cgi?id=1080822
Create one app(e.g., myphp53), embedded with postgresql-8.4/9.2, stop
postgresql db cartridge, found postgresql/pid/postgres.pid still
existing in rhcsh and even though prompts "Stopping postgresql-8.4 ...
done"
Merge pull request #5076 from bparees/postgresql_pid

Merged by openshift-bot