core: Changes to MockEJBStrategyRule

The following patch introduces the following changes:
1. Gives the ability to allow to mock a managed resource, not just a bean
2. mockBean should actually use Mocikto to define the actual mock using when..thenReturn as
the "startingMethod" was not aware to that bean when it was called

Change-Id: Ia23cbe33abe5a080cd599c6af468e3ce728c190a
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>