Make assignment of mPlugin members consistent

Before, it was possible for mPlugin, mPluginV1_1, and mPluginV1_2 to be
assigned to different plugins. Now, they are guaranteed to always point
to the same object. Also to be safe, mPlugin is set to NULL if there is
an initailization error.

Test: Run gts on blueline
Bug: 112386116
Bug: 121382196
Change-Id: Ie3ff7369e0c66d4502fab3f4a1d18b2882140143