FakeVim: Reset FakeVim properly after user command

If FakeVim mode is disabled, enable it just for the single requested
user command.

Keep useful messages shown for few seconds.

Task-number: QTCREATORBUG-10460
Change-Id: I89c1722542f47befbf2c24a663bf3d1c455b77d9
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>