Fix memory leak in WifiManager

Root Cause: ServiceHandler in WifiManager would be hold by the channel created in AsyncServiceHandler in WifiService.
Solution: Force closed when the connection is closed.

Change-Id: Id6e1774e619fb95918ed55e866653e79f47437b6
Signed-off-by: Zhijun Peng <pengzhj@marvell.com>
Merge branch 'master-cherry' into franco