build: ignore deactivated feeds

The OpenWrt feeds.conf.defaults contains some feeds that are commented out
and not active. Such feeds will be returned by the default_feeds.sh script
anyway and causing pseudo feeds. Limit the script to only return active
feeds, by filtering out lines starting with '#'.
This usually only applies to the OpenWrt master branch.

Signed-off-by: Sven Roederer <freifunk@it-solutions.geroedel.de>

change as per NeoRider

scripts/default_feeds.sh

-DEFAULT_FEEDS="$(awk '{print $2}' openwrt/feeds.conf.default)"
+# list feeds which don't start with #
+DEFAULT_FEEDS="$(awk '!/^#/ {print $2}' openwrt/feeds.conf.default)"