AVRCP: Stop Fast forward and fast rewind

In A2dpMediaBrowserService.java, fast forward and fast rewind
were not stopping after pressing fast forward or fast rewind
key again. The issue was coming due to the sending of "button pressed"
key event again after sending "button released". The fix
is done by adding a "return" after sending button released.

Test: Manual testing by pressing fast forward/fast rewind
and then pressing it again to stop the operation

Change-Id: I2dc9a4c83d150b5ab8cec1281444a911d372b819