Enforce VisualVoicemailService to require BIND_VISUAL_VOICEMAIL_SERVICE

Also fixes NPE in enforceVisualVoicemailPackage()

Change-Id: I6a9a6ea33fc939cf0926e9d5ec4beeb0f312e24c
Fixes: 35854031
Test: CTS - VisualVoicemailServiceTest
2 files changed