Make sure BluetoothSocket#connect throws on error.

It sometimes fails silently, resulting in callers using the socket
even though it hasn't been initialized.

http://b/13909270

Change-Id: Ied08982b51d44c3d2dec72785888ea6c6497a664

core/java/android/bluetooth/BluetoothSocket.java

@@ -325,6 +325,7 @@ public final class BluetoothSocket implements Closeable {
             }
         } catch (RemoteException e) {
             Log.e(TAG, Log.getStackTraceString(new Throwable()));
+            throw new IOException("unable to send RPC: " + e.getMessage());
         }
     }