Avoid deadlock in getIccSimChallengeResponse() when disposing IccRecords

The lock object 'mLock' must be cared in IccRecords.dispose() as there
might be another thread waiting in getIccSimChallengeResponse().
EVENT_AKA_AUTHENTICATE_DONE never comes to IccRecords.handleMessage() if
IccRecords has already been disposed. That is because such events are
ignored in handleMessage() of the derived classes.

Change-Id: I8b36d4b44bc07bf5281325fb759b7a8dac0a8a32