Keep verbose log statements, but silence them by default

Do not strip out ALOGV statements in production builds,
but keep them silent by setting the default log level
for AudioPolicyManager to D.

Bug: 113756665
Test: adb shell setprop log.tag.APM_AudioPolicyManager V
      check logcat for verbose log messages from APM
Change-Id: I0129a07e3afa11634945763b8d976699ce13093e