[usecase-webapi] Improve WebSpeech usecase

- Update the description for Connecting to speech server
- Failure analysis: Could not connect to speech server

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 0, fail 1, block 0
Merge pull request #696 from yunxliu/yunxliu/misc/webSpeech_modify

[usecase-webapi] Improve WebSpeech usecase