Separate address from netmask or prefix length before validation

The previous commits will help you start a pot that has been
configured with alias networking and addresses with netmasks or prefix
lengths, but stopping a pot may fail when it tries to remove addresses
from network interfaces.  If the netmask or prefix length is present,
ifconfig(8) won't like it very much when you try to `-alias`
a.k.a. `delete`.  So we parse the recorded addresses yet again in
order to ensure proper cleanup of network addresses.

Fixes bsdpot#268

share/pot/network.sh

@@ -279,7 +279,7 @@ _get_alias_ipv6()
 # $2 network stack
 _validate_alias_ipaddr()
 {
-	local _i _nic _ip _ipv4_empty _ipv6_empty _stack
+	local _i _nic _ip _ipv4_empty _ipv6_empty _stack _netmask
 	_stack="$2"
 	_ipv4_empty="YES"
 	_ipv6_empty="YES"
@@ -294,6 +294,12 @@ _validate_alias_ipaddr()
 		else
 			_ip="$_i"
 		fi
+		if echo "$_ip" | grep -qF '/' ; then
+			_netmask="$( echo "$_ip" | cut -f 2 -d '/' )"
+			_ip="$( echo "$_ip" | cut -f 1 -d '/' )"
+		else
+			_netmask=""
+		fi
 		if ! potnet ipcheck -H "$_ip" 2> /dev/null ; then
 			_error "$_ip is not a valid IP address"
 			return 1 # false

share/pot/stop.sh

@@ -75,6 +75,10 @@ _js_stop()
 				_nic="$POT_EXTIF"
 				_ipaddr="$_i"
 			fi
+			if echo "$_ipaddr" | grep -qF '/' ; then
+				_netmask="$(echo "$_ipaddr" | cut -f 2 -d '/' )"
+				_ipaddr="$(echo "$_ipaddr" | cut -f 1 -d '/' )"
+			fi
 			if potnet ip4check -H "$_ipaddr" ; then
 				if ifconfig "${_nic}" | grep -q "inet $_ipaddr " ; then
 					ifconfig "${_nic}" inet "$_ipaddr" -alias