[qmp-system] Update qmp_get_openwrt_default_network()

The qmp_get_openwrt_default_network function stopped working since
OpenWrt commit 892fc7caa9eee9f5ef9e172677f871c02841bae8, as parsing the
board.json wouldn't provide the defaults anymore.
Signed-off-by: Roger Pueyo Centelles <roger.pueyo@guifi.net>

packages/qmp-system/files/etc/qmp/qmp_functions.sh

@@ -371,7 +371,9 @@ qmp_get_openwrt_default_network() {
 
 	[ "$role" != "lan" ] && [ "$role" != "wan" ] && return
 
-	grep -A${flen} "network" $board_file | grep -A${flen} $role | grep -m 1 -B${flen} "}" | grep -m 1 "ifname" | cut -d ":" -f2 | sed -e 's/^[ \t]*//' | cut -d '"' -f 2
+	# Fix for #489 after introduction of UCI bridge model (OpenWrt >= 21.02)
+	#grep -A${flen} "network" $board_file | grep -A${flen} $role | grep -m 1 -B${flen} "}" | grep -m 1 "ifname" | cut -d ":" -f2 | sed -e 's/^[ \t]*//' | cut -d '"' -f 2
+	grep -A${flen} "network" $board_file | grep -A${flen} $role | grep -m 1 -B${flen} "}" | grep -m 1 "device" | cut -d ":" -f2 | sed -e 's/^[ \t]*//' | cut -d '"' -f 2
 }
 
 qmp_attach_device_to_interface() {