camera3: Don't try to disconnect stream native windows more than once

This fixes the multiple-disconnect-from-BufferQueue bug.

(In logs)
BufferQueue: [SurfaceView] disconnect: connected to another api (cur=0, req=4)

Bug: 9114681
Change-Id: I21ae1c5bd993701eea13648aa9994979a24eb210
diff --git a/services/camera/libcameraservice/camera3/Camera3Stream.cpp b/services/camera/libcameraservice/camera3/Camera3Stream.cpp
index 9c9c258..f05658a 100644
--- a/services/camera/libcameraservice/camera3/Camera3Stream.cpp
+++ b/services/camera/libcameraservice/camera3/Camera3Stream.cpp
@@ -258,7 +258,15 @@
 status_t Camera3Stream::disconnect() {
     ATRACE_CALL();
     Mutex::Autolock l(mLock);
-    return disconnectLocked();
+    ALOGV("%s: Stream %d: Disconnecting...", __FUNCTION__, mId);
+    status_t res = disconnectLocked();
+
+    if (res == -ENOTCONN) {
+        // "Already disconnected" -- not an error
+        return OK;
+    } else {
+        return res;
+    }
 }
 
 status_t Camera3Stream::registerBuffersLocked(camera3_device *hal3Device) {