Camera: Cleanup to prepare() implementation

- Mutexes _might_ be a good idea
- Don't be surprised by behavior that's expected
- Use the existing logging macros

Bug: 20537148
Change-Id: Ie62985a786d7e6645b4e4fe019dd98b02891a1f7
diff --git a/services/camera/libcameraservice/api2/CameraDeviceClient.cpp b/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
index 9c4f9cd..b6f6677 100644
--- a/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
+++ b/services/camera/libcameraservice/api2/CameraDeviceClient.cpp
@@ -691,15 +691,10 @@
         return BAD_VALUE;
     }
 
-    // Also returns BAD_VALUE if stream ID was not valid
+    // Also returns BAD_VALUE if stream ID was not valid, or stream already
+    // has been used
     res = mDevice->prepare(streamId);
 
-    if (res == BAD_VALUE) {
-        ALOGE("%s: Camera %d: Unexpected BAD_VALUE when preparing stream, but we"
-              " already checked and the stream ID (%d) should be valid.",
-              __FUNCTION__, mCameraId, streamId);
-    }
-
     return res;
 }