AudioTrack: Allow flush in flush state to clear subsequent written data

Fixes Photos a/v sync issue introduced by
commit 1d3556d6a0

Test: Photos, pause, then seek several times, then play.
Test: CTS AudioTrackTest, Bluetooth, Offload, Gallery, Play Music.
Bug: 79327282
Change-Id: I9de8edd88b526b5a9dbc9cd720bf725474949dfc

media/libaudioclient/AudioTrack.cpp

@@ -806,7 +806,7 @@ void AudioTrack::flush()
         return;
     }
     AutoMutex lock(mLock);
-    if (mState == STATE_ACTIVE || mState == STATE_FLUSHED) {
+    if (mState == STATE_ACTIVE) {
         return;
     }
     flush_l();