Changing BlockedNumbersAdapter to use Management container as parent

The blocked_number_fragment gets removed from the
BlockedNumbersSettingActivity when we change to the search view. Doing
so causes a crash when we attempt to show a Snackbar with that fragment
as the parent view. Instead we use the container for the Management
screen since it doesn't get removed.

Bug:26032803
Change-Id: I6b14447fa75eb2618f511799d4f947ab432611f9