Http remotes that do expose a git config file, but are not initialized
resulted in an ugly and unncessary error message, now sqelched.
When git-annex-shell configlist is run w/o the autoinit field, it may
not generate a uuid for the repository. So in that case, it's not
unexpected for the config it does list to not include a UUID, and
dumping out the config in a warning message is not needed.
If configlist is asked to autoinit and we don't get back a config with a
UUID in it, that suggests some problem, and what we got back may not be
a config at all but some diagnostic message, so it does make sense to
output it then.