detect docker image exists on remote without pull.
dockerimageexists -image ubuntu:18.04
# need auth
dockerimageexists -image some_private:tag -username $user -password $pwd
# output file (empty file currently) when found
dockerimageexists -image some_private:tag -outfile $filename image: wangpeiwen/dockerimageexists
settings:
username: someone
password: pwd
image: ubuntu:18.04
outfile: outfile