Puppet plugin: fix the 'require' in operatingsystem.rb

Previously, the patch did not surround it with quotes, leading
Ruby to attempt to parse "ovirt.rb" as a variable. Quote it so it
parses as expected.

Change-Id: I4a4c4cba3f46249c9b3c87d37657f648093414f2
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1003440
Signed-off-by: Ryan Barry <rbarry@redhat.com>