username check:fixed invalid tooltip show

1.username is valid , but when hover on the input div, the invalid tooltip will show again;
2.when username is invalid , but when click into the username input
div(without inputting,just click into), and the red input rect will hide

tower:https://tower.im/projects/17ce1bc3f1f14999931c914377f5af62/todos/f79e570343cc46d7902ffef24b3f30a8/

Change-Id: Ie37ba3a33949eac5219f881816ddf6d11cdcaa2b
Merge "username check:fixed invalid tooltip show"