hostid: Generate random UUID by default

This way MAC addresses are no longer exposed.

Discussed with:	bapt
MFC after:	3 days

libexec/rc/rc.conf

@@ -137,6 +137,7 @@ extra_netfs_types="NO"	# List of network extra filesystem types for delayed
 hostname=""			# Set this!
 hostid_enable="YES"		# Set host UUID.
 hostid_file="/etc/hostid"	# File with hostuuid.
+hostid_uuidgen_flags="-r"	# Flags to uuidgen.
 nisdomainname="NO"		# Set to NIS domain if using NIS (or NO).
 dhclient_program="/sbin/dhclient"	# Path to dhcp client program.
 dhclient_flags=""		# Extra flags to pass to dhcp client.

libexec/rc/rc.d/hostid

@@ -126,7 +126,7 @@ hostid_generate()
 	# Generate a random UUID if invalid or not found
 	if [ -z "${uuid}" ]; then
 		# If not found, fall back to software-generated UUID.
-		uuid=`uuidgen`
+		uuid=`uuidgen ${hostid_uuidgen_flags}`
 	fi
 	hostid_set $uuid
 }