audio policy: fix camera shutter sound

Fix regression in camera shutter sound when system stream
volume is 0.

Bug: 132696227
Test: repro steps in bug.
Test: regressions when camera sound is enforced
Change-Id: I76b4a5ee041f97c5f771c003bf4f99327d797096
diff --git a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
index c430488..575a6c2 100644
--- a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
+++ b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
@@ -777,6 +777,12 @@
     // check for device and output changes triggered by new force usage
     checkForDeviceAndOutputChanges();
 
+    // force client reconnection to reevaluate flag AUDIO_FLAG_AUDIBILITY_ENFORCED
+    if (usage == AUDIO_POLICY_FORCE_FOR_SYSTEM) {
+        mpClientInterface->invalidateStream(AUDIO_STREAM_SYSTEM);
+        mpClientInterface->invalidateStream(AUDIO_STREAM_ENFORCED_AUDIBLE);
+    }
+
     //FIXME: workaround for truncated touch sounds
     // to be removed when the problem is handled by system UI
     uint32_t delayMs = 0;
@@ -910,6 +916,13 @@
         }
         *dstAttr = mEngine->getAttributesForStreamType(srcStream);
     }
+
+    // Only honor audibility enforced when required. The client will be
+    // forced to reconnect if the forced usage changes.
+    if (mEngine->getForceUse(AUDIO_POLICY_FORCE_FOR_SYSTEM) != AUDIO_POLICY_FORCE_SYSTEM_ENFORCED) {
+        dstAttr->flags &= ~AUDIO_FLAG_AUDIBILITY_ENFORCED;
+    }
+
     return NO_ERROR;
 }