Try an experimental way to revert to keyword completion

Reverting to keyword completion should take place when any of the
special completions (user, omni, vim, dict, etc) did not return any
matches.

This is VERY Experimental at the moment, and may not be desirable.

Fix completion_tried condition when pop up menu is visible.

Revert "Fix completion_tried condition when pop up menu is visible."

This reverts commit bdc84ca53519a31dc1dd838baffd7d777515918e.