Fix logic bug in _should_finish.
Fix logic bug in _should_finish.

agonzalezro/flocker,agonzalezro/flocker,AndyHuu/flocker,AndyHuu/flocker,w4ngyi/flocker,mbrukman/flocker,mbrukman/flocker,wallnerryan/flocker-profiles,w4ngyi/flocker,hackday-profilers/flocker,agonzalezro/flocker,AndyHuu/flocker,hackday-profilers/flocker,wallnerryan/flocker-profiles,hackday-profilers/flocker,wallnerryan/flocker-profiles,mbrukman/flocker,w4ngyi/flocker