Fixed normal bug EXT-5885 ([HARD CODED] - The busy response should be localized. hard coded in llviewermessage.cpp).

- It wasn't hardcoded in llviewermessage.cpp, but xml which contains it is not localizable. Added string with default busy message to strings.xml
and used it in LLFloaterPreference::cleanupBadSetting().

--HG--
branch : product-engine