generic userid: use the new USERID api

recent changes in trunk allow us to specify the userid inside the openwrt makefile.
the info is stored int he meta data of the IPK contorl file and users are generated
by the new generic postinst trigger.

Signed-off-by: John Crispin <blogic@openwrt.org>

net/prosody/Makefile

@@ -28,6 +28,7 @@ define Package/prosody
   DEPENDS:=+luafilesystem +libidn +luaexpat +luasec +libopenssl +libidn +liblua 
   TITLE:=XMPP server
   URL:=http://prosody.im/
+  USERID:=prosody=54:prosody=54
 endef
 
 define Package/prosody/description

net/prosody/files/prosody.init

@@ -14,8 +14,6 @@ RUN_USER=prosody
 RUN_GROUP=prosody
 
 start() {
-	user_exists prosody 54 || user_add prosody 54
-	group_exists prosody 54 || group_add prosody 54
 	[ -d /var/run/prosody ] || {
 		mkdir -m 0755 -p /var/run/prosody
 		chown prosody:prosody /var/run/prosody