Fix work tab is gone when leaving search mode

1. onSearchResultsChanged is not called if the query is empty.
   Introduce onClearSearchResult and restore the tab there
2. rebindAdapters should only perform the actual logic
   if showTabs != mShowTabs, except the first time when we init the
   layout in onFinishInflate.

Fix: 71737947
Change-Id: I5485d6be0fc33b73aa6e0709be66cef8d43b4dbd