Pull up the following revisions(s) (requested by spz in ticket #1891):
	sys/kern/uipc_syscalls.c:	revision 1.163

If the unix socket is closed before accept, the mbuf returned by
m_get() will have an uninitialized length and contain junk from a
previous call. Initialize m_len to be 0 to handle this case.
Fixes PR/47591
Ticket #1891