[webapi]Change ref test in tct-flexiblebox-css3-tests

- Add 2 reference files for 19 tests
- Still keep the 19 ref tests as manual because test tool haven't support ref type

Impacted tests(approved): new 0, update 19, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 19, fail 0, block 0