Add very limited support for the isc-dhclient. It will almostly certaintly

only work if there's just one interface doing dhcp.  This version implements
the same logic as the version in the PR, but uses pgrep to be less verbose.

PR:		conf/95905
MFC after:	1 week

etc/rc.d/dhclient

@@ -26,6 +26,10 @@ dhclient_start()
 			if [ -n "$pids" ]; then
 				exit 0
 			fi
+		elif [ -e /var/run/dhclient.pid ]; then
+			if [ -n "`pgrep -F /var/run/dhclient.pid`" ]; then
+				exit 0
+			fi
 		fi
 	fi