s:clean_make_info: assert that there are no queued jobs/makes (#1573)
s:clean_make_info: assert that there are no queued jobs/makes (#1573)

Closes https://github.com/neomake/neomake/pull/1567.
euclio/neomake,neomake/neomake,euclio/neomake,nerdrew/neomake,nerdrew/neomake,neomake/neomake,codeinabox/neomake