collectd: move jshn.sh include to remove warning

Redmine-patch-id: 3680
If I build an image with the imagebuilder I get the following output
during image building:

../root-x86/etc/init.d/collectd: line 4: /usr/share/libubox/jshn.sh:
No such file or directory

To remove this messsage move include to the needed postion, so that the
message does not occur during image building on the host system anymore.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
(cherry-picked, modified to match 19.07)
Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

utils/collectd/files/collectd.init

 #!/bin/sh /etc/rc.common
 # Copyright (C) 2006-2016 OpenWrt.org
 
-. "/usr/share/libubox/jshn.sh"
-
 START=80
 STOP=10
 
@@ -62,6 +60,7 @@ process_generic() {
 
 	local config=""
 
+	. /usr/share/libubox/jshn.sh
 	json_init
 	json_load_file "$json"