samba4: fix missing busybox 'hostname -f' command

* busybox does not have 'hostname' by default so replaced it with uci calls

Signed-off-by: Andy Walsh <andy.walsh44+github@gmail.com>

net/samba4/files/samba.init

@@ -21,7 +21,9 @@ smb_header() {
 
 	local workgroup description charset
 	# we dont use netbios anymore as default and wsd/avahi is dns based
-	local hostname="$(hostname -f)"
+	local hostname="$(uci get system.@system[0].hostname)"
+	local domain="$(uci get dhcp.@dnsmasq[0].domain)"
+	[ -n "$domain" ] && hostname="$hostname.$domain"
 
 	config_get workgroup		$1 workgroup	"WORKGROUP"
 	config_get description		$1 description	"Samba on OpenWrt"