Mms: Fix Multi-thread "read" button/intent

Works, but I'd like to get delete
going as well.  Delete works as well
but threads become locked into an "unread"
state until you send through that thread
again.  Odd stuff all over with inconsitent
behavior.

PS2: Ammendment of logic
PS3: Remove attempt at delete logic
    Instead (for now) refuse to let delete
    button show up for multi-thread notifications
    That'll be another patchset if deletion can
    be made functional for even single-thread
    messages.
PS4: Derp

Change-Id: Ic04c5ea7f738958a5d4f6f6d92e5952dd5298b6b