Added some tests for relative nonexistent dirs to open.
Added some tests for relative nonexistent dirs to open.

bf4/fakefs,openSUSE/fakefs,1234-/fakefs,dekz/fakefs,fakefs/fakefs,bquorning/fakefs,marxarelli/fakefs,anthonyryan1/fakefs,eventualbuddha/fakefs,onehub/fakefs,vhl/fakefs,pivotal-cf-experimental/fakefs,zimbatm/fakefs,lgierth/fakefs,deployable/fakefs,defunkt/fakefs,moretea/fakefs