AudioService: conditional logging of hearing aid volume

To avoid confusion when reading audio dumpsys, do not log
hearing aid volume changes when a DEVICE_OUT_HEARING_AID is
not connected.

Bug: 236983951
Test: adb shell dumpsys audio | grep HEARING_AID
Merged-In: I36f39e88e11f4e8ed644b54bfb15308f08a3d698
Change-Id: I36f39e88e11f4e8ed644b54bfb15308f08a3d698
(cherry picked from commit 7ea873b0)