ci: do not add assignees if already set

If PR already has an assignee, do not add additional assignees to the
PR. Each PR should only have one assignee (in most cases)

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

scripts/set_assignees.py

@@ -170,7 +170,7 @@ def process_pr(gh, maintainer_file, number):
 
     ms = []
     # assignees
-    if maintainer != 'None':
+    if maintainer != 'None' and not pr.assignee:
         try:
             u = gh.get_user(maintainer)
             ms.append(u)
@@ -181,6 +181,8 @@ def process_pr(gh, maintainer_file, number):
             log(f"Adding assignee {mm}...")
             if not args.dry_run:
                 pr.add_to_assignees(mm)
+    else:
+        log("not setting assignee")
 
     time.sleep(1)