aaudio: fix crash on disconnect for shared streams

This fixes a regression caused by ag/12396646
That CL changed the way that AudioStreams are managed
using android::sp<>. Unfortunately it caused
a crash in audioserver when shared streams were disconnected.
The root cause was calling disconnectedRegisteredStreams()
from a data processing thread, which resulted
in deleting the object while the thread was using it.

The call was unnecessary so it was removed.

Bug: 161914201
Bug: 163165126
Bug: 164411271
Bug: 166877425
Test: adb logcat *:F
Test: Use OboeTester TEST DISCONNECT
Test: See b/166877425 for more details
Change-Id: I30fc7f00061a9caf5e3d9f7c8e257102c34f9d92
Merged-In: I30fc7f00061a9caf5e3d9f7c8e257102c34f9d92