retrigger: Allow to specify the manifest's remote identifier in a variable

Costum manifest may override this variable

manifest.yml

@@ -27,6 +27,11 @@ variables:
   # Using variable here, to allow override in other projects
   # including this file
   MANIFEST_PROJECT_ID: 1725
+  # In the manifest, the remotes are specified by an identifier
+  # This is used to find out included projects for the retrigger
+  # job. In costum manifests, the remote may be named differently
+  # so we need a variable that may be overriden.
+  CI_PARAM_SECO_REMOTE: seco-ne
 
 workflow:
   rules:
@@ -57,7 +62,7 @@ retrigger:
     - PROJECTS=$(
         .gitlab-ci/scripts/get_manifest_projects.py
         --manifest=default.xml
-        --remote=seco-ne
+        --remote=${CI_PARAM_SECO_REMOTE}
         --concat-namespaces
       )
     # Add the gitlab-ci project