ipfilter 5.1.2 (vs 4.1.28 in previous releases of FreeBSD) stores IPv4

and IPv6 rules in a single table. ipf -6 -Fa will flush the whole table,
including IPv4 rules. This patch removes the redundant ipf -I -6 -Fa
statement.

PR:		188318
MFC after:	2 weeks

etc/rc.d/ipfilter

@@ -65,7 +65,6 @@ ipfilter_reload()
 			err 1 'Load of rules into alternate set failed; aborting reload'
 		fi
 	fi
-	${ipfilter_program:-/sbin/ipf} -I -6 -Fa
 	if [ -r "${ipv6_ipfilter_rules}" ]; then
 		${ipfilter_program:-/sbin/ipf} -I -6 \
 		    -f "${ipv6_ipfilter_rules}" ${ipfilter_flags}