[webapi][XWALK-2344] Update test step for gamepad

- To fire gamepadconnected event, need reconnect gamepad.

Impacted TCs num(approved): New 0, Update 3, Delete 0
Unit test Platform: Andriod
Unit test result summary: Pass 3, Fail 0, Blocked 0
Merge pull request #722 from JianfengXu/xujf/2344

[webapi][XWALK-2344] Update test step for gamepad