Make provider to wait for rabbitmq cluster

W/o this fix, then RabbitMQ put in a cluster and managed
by Pacemaker, rabbitmqctl/rabbitmqadmin can fail their
requests due to cluster is not ready yet.

The solution is to introduce a module with a common function wait_for_rabbitmq. 
And include it as a class methods for
providers to ensure rabbitmqctl or rabbitmq_admin call will
retry instead of fail then cluster is not ready.

Co-authors: Dmitry Ilyin <dilyin@mirantis.com>
Closes-bug: #MODULES-1452

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Done.
For some strange reason class inheritance doesn't work in lib/puppet/provider/rabbitmq_exchange/rabbitmqadmin.rb. So, I had to use an old method there as well...
And because of that rabbitmqadmin.rb one, I had to introduce one more file to maintain both approaches.