Fix blacklist preferences fragment transition for tablets.

Change-Id: Iecde099b111ae31c8e11ce366d9d06d965029ed7
Fix confusing warning dialog behaviour.

The settings app closing when pressing back while the dialog is shown or
clicking outside of the dialog was confusing for the user. Instead, make
sure the user has to acknowledge the dialog.

Change-Id: I8ffdf6a2ede8b67176fd22a13d7046a707b52b89