Revert "Use "baseurl" property instead of "url" to work with new copr-frontend"

This reverts commit 9e7b55c54c.

The modified version only works on copr-be-dev, production instance
needs the old version of the mock.cfg.j2 file

roles/copr/backend/files/provision/files/copr-rpmbuild/mock.cfg.j2

@@ -29,7 +29,7 @@ config_opts['{{ pkg_manager_conf }}.conf'] += """
 {% for repo in repos %}
 [{{ repo["id"] }}]
 name='{{ repo["name"] }}'
-baseurl={{ repo["baseurl"] }}
+baseurl={{ repo["url"] }}
 gpgcheck=0
 enabled=1
 skip_if_unavailable=1