Show list of all phone numbers for empty query.

+ Configure BlockedListSearchFragment so it will not show empty
when the search query is null.
+ Removed local reference and equality check for changes in the
query string. This is done in the superclasses already, so was
redundant.
- Removed unnecessary override in RegularSearchFragment.

Bug: 24910704
Change-Id: Ifd11eed9e3ba6fb00ba535ae019df477f81518fb