audio: optimize spatializer activation

Only enable the spatializer effect engine when the requested
level is not none and there are active playback clients.

Also set max update period to 1 second instead of 50ms when creating
the head pose controller as there is no need to wake so often if no
audio is processed by the spatializer effect.

Also add a missing forwarded of the head tracking mode to the engine
when the actual mode changes

Bug: 227740874
Test: make
Change-Id: I05a6f4e9edea319e300e98a33dc3a3fd78143466