s4-smbd: Also restart prefork children lost to SIGKILL (-9)

s4-smbd: Also restart prefork children lost to SIGKILL (-9)

Samba 4.10 and later versions have a process restart capability to greatly
reduce the impact of crashes due to a NULL pointer de-reference or abort().

However SIGKILL was deliberatly omitted.

Sadly this is the most likely case, due to the OOM killer, as raised here:

https://lists.samba.org/archive/samba-technical/2019-November/134529.html

Subsequent discussion (offline) has been to agree that we should restart in
this case.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14221

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>