autobuild: don't cleanup the pid file within the retry loop

if we rebase and retry we need to keep the pid file

script/autobuild.py

@@ -278,7 +278,6 @@ def write_pidfile(fname):
     f = open(fname, mode='w')
     f.write("%u\n" % os.getpid())
     f.close()
-    cleanup_list.append(fname)
 
 
 def rebase_tree(url):
@@ -473,6 +472,8 @@ while True:
         cleanup()
         raise
 
+cleanup_list.append(gitroot + "/autobuild.pid")
+
 blist.kill_kids()
 if options.tail:
     print("waiting for tail to flush")