filter: Tweak the autocompletion behaviour on <Enter>

filter: Tweak the autocompletion behaviour on <Enter>

No patch has landed yet and we've already had feedback from users (which
is a good thing!) that didn't want to lose the "quick" submitter search
by just typing a string and pressing <Enter> without having to wait for
the autocompletion to finish.

This will also make <Enter> do something useful for input strings that
have fewer than 4 characters, the autocompletion query only triggers
after that.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Stephen Finucane <stephen.finucane@intel.com>