Safer client config for admins

While I did not break production I was intending till until I read the script.

Suggest that admins make their client configuration prod safe.

docs/koji/safeclient.md

+# Avoid using production as default
+
+For koji admins who are frequently running commands such as `koji add-tag` on test koji instances it can be dangerous to have the client use the default koji service in `/etc/koji.conf` as the production service.
+
+To override the default configuration file create a file `~/.config/koji/prod.conf` containing:
+
+```ini
+[koji]
+server = https://useprodprofile.cern.ch/kojihub
+weburl = https://useprodprofile.cern.ch
+topurl = https://useprodprofile.cern.ch/kojifiles
+topdir = https://useprodprofile.cern.ch/kojifiles
+authtype = kerberos
+
+[prod]
+server = https://kojihub.cern.ch/kojihub
+weburl = https://koji.cern.ch
+topurl = https://koji.cern.ch/kojifiles
+topdir = https://koji.cern.ch/kojifiles
+authtype = kerberos
+```
+
+Once done the production profile must be explicitly specified with `koji -p prod`. All koji commands will fail unless a profile is specified.