[webapi][XWALK-893] Add 6 Tcs and update 24 Tcs for iap
- Modify the way of using iap
- Failure analysis: The restore method does not suppot
- Block analysis: "In App Purchase" feature does not allowed in China

Impacted tests(approved): new 6, update 24, delete 0
Unit test platform: [Android]
Unit test result summary: pass 6, fail 2, block 22
Merge pull request #378 from yunxliu/yunxliu/webapi/rewrite_iap_Tcs

[webapi][XWALK-893] Add 6 Tcs and update 24 Tcs for iap