Fixes #6543 - updt index on cp event bz1115602

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.
This looks like it would be a nice addition to ForemanTasks to allow checking if a task is already running.