RabbitMQ: Simplify how to suppress error from pam_unix.so
RabbitMQ: Simplify how to suppress error from pam_unix.so

This is follow-up of 44985bd42d21ce705387c01b188f27711791f51f, and
replaces the implementation to suppress error from pam_unix.so by
the quiet option, as CentOS 7/RHEL 7 support was removed a long ago.

Change-Id: I620f96dc21c5bc85b14152e92c79b648c4a1b343

openstack/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo