require attr from pam_openshift

Fixes bz973377

In the (exceedingly unlikely) case that the "attr" RPM isn't installed,
oo-namespace-init will bomb trying to set appropriate attributes. "attr" is in
the minimal install but at least one customer managed to run into this, so
might as well make it explicit.
Merge pull request #2822 from calfonso/master

Merged by openshift-bot