CVE-2022-37966 python:/tests/krb5: call sys.path.insert(0, "bin/python") before any...

CVE-2022-37966 python:/tests/krb5: call sys.path.insert(0, "bin/python") before any other imports

This allows the tests to be executed without an explicit
PYTHONPATH="bin/python".

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15237

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Tue Dec 13 14:06:14 UTC 2022 on sn-devel-184