`docker image rm -f` should exit with 1 if the image was not removed

[dnephin]

This was changed in #160, but there are some problems with this new behaviour.

rm -f /some/file still exits with 1 if you don't have permission to remove it.
docker image rm -f should exit with 1 if the image was not removed.

[dnephin]

cc @thaJeztah @vieux

[thaJeztah]

ah, yes, if it failed to remove it should exit with 1, if the image did not exist in the first place, we can ignore; does that SGTY?

[dnephin]

Yes, that sounds correct to me

[adshmh]

#dibs

[abhinavkorpal]

I am not able to clean the /var/lib/docker/overlay ...Any suggestion should i get ?

[eiais]

@dnephin I think this should have been closed after #654 merged.

[dnephin]

yup, thanks!