script/autobuild.py: let cleanup() ignore errors from rmdir_force() by default

script/autobuild.py: let cleanup() ignore errors from rmdir_force() by default

It's not useful to generate a python backtrace from within the cleanup code.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14628

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
(cherry picked from commit 9883ac45939f253a63f3ff312fc3912c5f02cdac)

Autobuild-User(v4-14-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-14-test): Tue Feb  2 10:29:44 UTC 2021 on sn-devel-184

(cherry picked from commit cc1568be4d4250390a9ad03c84f5e260fc7acffd)