Do not add service credential url paramter if not necessary

[felixsch]

In normal RMT environments, zypper services do not need a ?credentials URL parameter since the repository path is not authenticated.
So do not add it and allow yum to work with RMT for SLL7

part of: https://trello.com/c/BSMxlGDN/3166-help-liberty-team-get-suseconnect-working-on-liberty-7

How to review this pull request:

$ cd <rmt>
$ git checkout no-credentials-in-service-url
$ rails server

# another terminal
$ docker run --rm -it --network=host registry.suse.com/suse/sle15:15.4
> zypper in -y suseconnect-ng curl tidy
> SUSEConnect --url http://localhost:4224
> cat /etc/zypp/credentials.d/SCCcredentials
> curl -u <username:password> http://localhost:4224/services/2292 | tidy -xml -iq 
# expect: There is no `?credentials=XXX` in the repo.url

If you have any questions, please do not hesitate to reach out to me! 🚀

Thank you!

[felixsch]

@jesusbv is looking into if it is possible to remove ?credentials= from the zypper_auth engine. Thank you

[ngetahun]

Pubcloud tests seem to be broken

[jesusbv]

@jesusbv is looking into if it is possible to remove ?credentials= from the zypper_auth engine. Thank you

@felixsch I have checekd and we do need the credentials

[ngetahun]

LGTM, tested with given demo instructions

[suse-tests-pass]

Well Done! Your tests are still passing.
https://ci.suse.de/job/scc-RMT-integration-tests/355609/console
If the given link has expired,you can force a Prophet rerun by just deleting this comment. (Merged 3b28555 into 024478b)