update gitlab user in override.conf

debian/postinst

@@ -267,7 +267,9 @@ case "$1" in
         path=/etc/systemd/system/gitlab-${service}.service.d
         mkdir -p $path
         if [ -e $path/override.conf ]; then
-          echo "$path/override.conf already exist" 
+          echo "$path/override.conf already exist"
+          # Make sure only gitlab user is updated
+          sed -i "s/^ *User=.*/User=$gitlab_user/" $path/override.conf
         else
           printf "[Service]\nUser=${gitlab_user}\n" > $path/override.conf
         fi