jenkinsfile: update from master branch

Change-Id: I2e5736d4304bb841c8ec86d883b7bc0641669881

Jenkinsfile

@@ -136,7 +136,8 @@ See https://wiki.savoirfairelinux.com/wiki/Jenkins.jami.net#Configuration_client
 
             steps {
                 sh """git checkout ${params.CHANNEL}
-                      git merge --no-commit FETCH_HEAD
+                      # Submodules are generally not managed by merging
+                      git merge -X theirs --no-commit FETCH_HEAD || git add `git diff --name-status --diff-filter=U | awk '{print \$2}'`
                    """
             }
         }