Calling as system when filtering VVM SMS in CarrierSmsFilterCallback

When the callback is invoked in CarrierSmsFilterCallback, the calling
identity is replaced with the carrier app.

VisualVoicemailSmsFilter need to be called from the system so the
calling identity must be restored before calling.

Change-Id: I03ad92aaefba58c57e76317cb30565a794a1c268
Fixes:28982677