s3:smb2_server: avoid segfault in smbd_smb2_request_pending_queue()

s3:smb2_server: avoid segfault in smbd_smb2_request_pending_queue()

Because we should not call smbd_smb2_request_error() on an
request that is still running.

If the subreq implementes a cancel function, this should
take care of triggering smbd_smb2_request_error.

metze

Signed-off-by: Michael Adam <obnox@samba.org>
(cherry picked from commit 9249871f40aab021d62d3154f8ca286b52f5ef76)

Signed-off-by: Stefan Metzmacher <metze@samba.org>
(cherry picked from commit d7910716920a324e0bba962241dd9b362d38d2b2)