[webapi] Update tests.xml format and change block case potion

- One case is block, becase of some case affect it, so put it in first potion.
- Format tests.xml

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: Tizen IVI
Tizen test result summary: Pass 1, Fail 0, Blocked 0
Merge pull request #465 from xinliux/xinliux/webapi/works-block

[webapi] Update tests.xml format and change block case potion