Actually check for READ_PHONE_STATE permission for Voicemail query

We were not checking READ_PHONE_STATE permission when callers
were querying for the number of voicemails the user had for a
subscription.

Removes old ITelephony#getVoiceMessageCount method from graylist
because it hasn't been used since kitkat and does not allow for
READ_PHONE_STATE permission checks.

Bug: 119884553
Test: manual
Change-Id: Ic6c29b123e192caf663d0e0c8da559116d1a78c9