Add a safety belt assignment to the nfsd for when "-p" isn't specified.

The kernel code assumes that nfsdargs.addr == NULL and nfsdargs.addrlen == 0
when there is no "-p" argument used for starting the nfsd.
This small patch ensures this is the case. In practice, I believe this always
happened, since "nfsdargs" was the last element on the stack for "main()",
but this little patch ensures it will be the case.
Spotted by inspection while adding a new optional field for "-p".

usr.sbin/nfsd/nfsd.c

@@ -180,6 +180,8 @@ main(int argc, char **argv)
 	struct nfsd_nfsd_args nfsdargs;
 
 	nfsdargs.mirrorcnt = 1;
+	nfsdargs.addr = NULL;
+	nfsdargs.addrlen = 0;
 	nfsdcnt = DEFNFSDCNT;
 	unregister = reregister = tcpflag = maxsock = 0;
 	bindanyflag = udpflag = connect_type_cnt = bindhostc = 0;