[address-book-app] fast scroll overlays header when search is invoked

[Olga Kemmet]

Steps to reproduce:

1. Launch address book app
2. Scroll through contacts to invoke fast scroll
3. Hit the search icon in the top right of the header while fast scroll letters are visible on screen

Actual result:
Fast scroll index moves up, overlaying the header. The invoked search field seems to be too short as well, not using the whole width of the header.

Expected result:
When SEARCh is invoked, fast scroll should disappear from view and the search input field has to use the whole width of the header.