Revert "Revert "AudioFlinger: Keep track of music effect thread ..."

Revert submission 26624467-revert-25712917-SEPJYAPZTA

Reason for revert: b/330202134 fixed with ag/26627359

Reverted changes: /q/submissionid:26624467-revert-25712917-SEPJYAPZTA

Change-Id: I0a43627e18368f3b883e9d3e33d60d679f2920d5
diff --git a/services/audioflinger/Effects.h b/services/audioflinger/Effects.h
index 46c44a6..5e527d3 100644
--- a/services/audioflinger/Effects.h
+++ b/services/audioflinger/Effects.h
@@ -616,7 +616,9 @@
             mThreadType = thread->type();
             mAfThreadCallback = thread->afThreadCallback();
         }
-
+        bool hasThreadAttached() const {
+            return thread().promote() != nullptr;
+        }
     private:
         const wp<IAfEffectChain> mChain;
         mediautils::atomic_wp<IAfThreadBase> mThread;