hammerhead: Fix bluetooth UART device perms

Change-Id: I19b636709b7172e66372faaa28e2b3c4c224621f
hammerhead: Make proximity check opt-in

This function's behavior is annoying and can even be
a deal-breaker for new or undiscerning CM users.

Change-Id: I51e43fd2adeaab79e74541fafadac95e16b267ff
hammerhead: Set volume last to avoid pops on speaker

Change-Id: I11b3d3c41f014628ac5899d3a3bfea1b7937d7bc