Copy ic_menu_search.png to ic_search_category_default.png

For some reason both these icons are exposed. Some apps use
ic_search_category_default.png for their search menu item,
and some use ic_menu_search.png. To make them look the same,
I copied ic_menu_search to ic_search_category_default.

Fixes http://b/issue?id=2373762

Change-Id: I045efaac84ed9507c4c0c9d6996f1bedb50d753f