Fixes #6543 - updt index on cp event bz1115602

DON'T MERGE UNTIL SQUASH and 
https://github.com/Katello/puppet-qpid/pull/8
https://github.com/Katello/puppet-katello_devel/pull/14
https://github.com/Katello/puppet-katello are merged 

This listens for entitlement events from candlepin and updates the specific
pool index instead of pulling all the subscription information each time
the user accesses the subscriptions page.

New gem dependency added: qpid_messaging
gem has dependency qpid-cpp-client-devel and qpid-cpp-client
rpm packages.
Good question and unfortunately I don't have a good answer. Maybe you could do something like `defined?(Rails::Server)` but I'm not sure if that would work in with Passenger.