[wrt] update wrt-webfeature-tizen-tests update xwalk command

[Detailed commit message]
Impacted TCs num(approved): New 0, update 1, deleted 0
Unit test platform: [tizen]
Unit test result summary: Pass 1 , Fail 0, Blocked 0
Merge pull request #439 from linshen/update-xwalk-listfeat

[wrt] update wrt-webfeature-tizen-tests update xwalk command