copr-builders: double escape maint.ini.j2 contents

- first escape for jinja
- second escaepe for copr-rpmbuild config reader

Then, the finall rpkg.conf content should look like:
download_url = https://${git_props:remote_netloc}/repo/pkgs/%(repo_path)s/%(filename)s/%(hashtype)s/%(hash)s/%(filename)s

roles/copr/backend/templates/provision/copr-rpmbuild/main.ini.j2

@@ -32,7 +32,7 @@ distgit_clone_url = https://src.stg.fedoraproject.org/%(module)s
 
 [main]
 frontend_url = {{ frontend_base_url }}
-distgit_lookaside_url = https://${git_props:remote_netloc}/repo/pkgs/%(repo_path)s/%(filename)s/%(hashtype)s/%(hash)s/%(filename)s
+distgit_lookaside_url = https://${% raw %}{{git_props:remote_netloc}}{% endraw %}/repo/pkgs/%(repo_path)s/%(filename)s/%(hashtype)s/%(hash)s/%(filename)s
 distgit_clone_url = {scheme}://{netloc}/%(repo_path)s
 rpm_vendor_copr_name = {{ rpm_vendor_copr_name }}