Fail when ssl parameters are missing and rabbit_use_ssl is set to true

This commit causes the run to fail is rabbit_use_ssl parameter is set
to true but the ssl related parameters remains undef.

Change-Id: Idd40601fe4a632204fdde120b857d0e22b6a2aed
(cherry picked from commit 55cbdace1730a3cb0af780ab9f7be703ac873eab)