tests: serialize: improve "Neomake#Make cancels previous jobs"
tests: serialize: improve "Neomake#Make cancels previous jobs"

Closes https://github.com/neomake/neomake/pull/1276.

euclio/neomake,nerdrew/neomake,neomake/neomake,euclio/neomake,neomake/neomake,nerdrew/neomake,codeinabox/neomake