fix return value for watch_tasks

cli/koji

@@ -441,6 +441,7 @@ def watch_tasks(session,tasklist,quiet=False):
     if not quiet:
         print("Watching tasks (this may be safely interrupted)...")
     sys.stdout.flush()
+    rv = 0
     try:
         tasks = {}
         for task_id in tasklist:
@@ -484,6 +485,7 @@ def watch_tasks(session,tasklist,quiet=False):
 Running Tasks:
 %s""" % (progname, '\n'.join(tlist)))
         raise
+    return rv
 
 def watch_logs(session, tasklist, opts):
     global options