net/iproute2: POSIX sh compatability: ${x/a/b} invalid

The ${x/a/b} shell construct is NOT defined in the POSIX specification,
it's a bash addition.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

net/iproute2.sh

@@ -138,7 +138,7 @@ _add_address()
 
 	# figure out the broadcast address if it is not specified
 	# This must NOT be set for IPv6 addresses
-	if [ "${address/:}" = "${address}" ]; then
+	if [ "${address#*:}" = "${address}" ]; then
 		[ -z "$broadcast" ] && broadcast="+"
 	elif [ -n "$broadcast" ]; then
 		eerror "Broadcast keywords are not valid with IPv6 addresses"