[ivi-tct][webapi] Avoid add testharness repeatedly

- In some tests, testharness.js has been added by unitcommon.js, add testharness.js repeatedly will create a timeout result, so update it following unitcommon.js

Impacted tests(approved): new 0, update 0, delete 0
Unit test platform: [IVI]
Unit test result summary: pass 188, fail 18, block 1
Merge pull request #1498 from haoxli/tct/webapi/tizen-systeminfo-update

[ivi-tct][webapi] Avoid add testharness repeatedly