UI: fix keyboard appearance.

This patch fixes two problems:
- during creation an account a screen could become not scrollable and
keyboard overly button "Create Account"
- keyboard shortly overly messages when appearing on a conversation
screen.

Change-Id: Ibcea9e1b6e933739cae9c2d2ae27337a3228ed45
Reviewed-by: Andreas Traczyk <andreas.traczyk@savoirfairelinux.com>