Do not force provider in rabbitmq base profile

We cannot force the provider when defining the rabbitmq_user on
stack update operation, because otherwise the noop_resource [1]
function cannot override the resource behaviour and the config
generation fails with unexpected calls to /usr/bin/rabbitmqctl.

We don't need to force the provider, so stop doing so.

[1] tripleo/lib/puppet/parser/functions/noop_resource.pp

Change-Id: If718dd50147b3430f9f72fa59c297ae65440f71a
Closes-Bug: #1739771

manifests/profile/base/rabbitmq.pp

@@ -163,7 +163,6 @@ class tripleo::profile::base::rabbitmq (
       # called explicity, if the rabbitmq service is already running.
       rabbitmq_user { $rabbitmq_user :
         password => $rabbitmq_pass,
-        provider => 'rabbitmqctl',
         admin    => true,
       }
     }