Messages printed when no UI is connected (e.g. memres) are currently lost.
Use the existing queue mechanism to queue these until a UI attaches, then
replay them. This isn't ideal but better than the current situation of
losing them entirely.
(Bitbake rev: cb241fb8544dfb05646dbae1a1b04e17878a466c)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>