use fully-qualified path to psql to set password

When setting the a user's password, use the fully qualified path to the
psql binary. This should fix #359
Merge pull request #365 from igalic/psql_path

use fully-qualified path to psql to set password
This fixes this test to work in the face of oppressive SELinux!
Merge pull request #368 from apenney/selinux-changes

This fixes this test to work in the face of oppressive SELinux!