package/avahi: fix GNUism in S05avahi-setup.sh

This script uses "chown user.group" instead of the POSIX "chown
user:group".  The first syntax is a deprecated GNU extension.
Since coreutils 9.1, chown started issuing a warning when this syntax is
used¹.

The result is that if both avahi and coreutils are enabled, this message
appears during boot:

chown: warning: '.' should be ':': 'avahi.avahi'

[1] https://git.savannah.gnu.org/cgit/gnulib.git/commit/lib/userspec.c?id=23cca8268d21f5d58ed0209002d5673d0518c426

Signed-off-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/avahi/S05avahi-setup.sh

@@ -5,7 +5,7 @@ case "$1" in
 	if [ ! -d /tmp/avahi-autoipd ]; then
 	    rm -rf /tmp/avahi-autoipd
 	    mkdir /tmp/avahi-autoipd
-	    chown avahi.avahi /tmp/avahi-autoipd
+	    chown avahi:avahi /tmp/avahi-autoipd
 	fi
 	;;
     stop) ;;