[package] ez-ipudate: fix config generator to permit default server

This patch allows ez-ipupdate to use the default server for the specified DDNS
service type when no server hostname is supplied by the user.

In detail:

The default config file supplied in the ez-ipupdate package does not include a
"server" line, and ez-ipupdate itself does not require an explicit server
(since it will select a server based on the service type).

Unfortunately, if the user simply fills in the blanks in the OpenWrt-supplied
ez-ipupdate config, the service will silently fail to start because the hotplug
 script inserts a line in the generated config which states "server=", and
ez-ipupdate doesn't like a blank server setting.

The above scenario doesn't seem like a good user experience, so this is a
small patch to the hotplug script to omit the "server" line (and let
ez-ipupdate select its own default) in the event that the user has not
specified a server.

Signed-off-by: Scott Dudley <spmsink@hotmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@20783 3c298f89-4303-0410-b956-a3cf2f4a3e73

net/ez-ipupdate/files/ez-ipupdate.hotplug

@@ -45,9 +45,13 @@ case "$ACTION" in
 					    config_get hostname $cfg hostname
 					    service=${service:-"dyndns"}
 					    config_get server	$cfg server
+					    server_line=""
+					    [ -n "$server" ] && {
+						server_line="server=$server"
+					    }
 					    cat > $config <<EOF
 service-type=$service
-${server:+server=$server}
+$server_line
 user=$username:$password
 host=$hostname
 cache-file=$cache