Mms: Cursor doesn't appear when pressing up/down/right/left key

When pressing up/down/right/left key on the keypad, the cursor
doesn't appear in the messagebox.
This is because the layout container is not focusable.

Change-Id: I82bfb417ce3b12ec55b5d8058e866282ab2dc66a
Author: b533 <b533@borqs.com>
Signed-off-by: edingX <erjunx.ding@intel.com>
Signed-off-by: Xiaokang Qin <xiaokang.qin@intel.com>
Signed-off-by: Beare, Bruce J <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 23638