_devel_backend.sh: add using config from `export "$NODEJS_CONFIG"`

```sh
user@sh$ NODEJS_CONFIG=`cat <$HOME/.supro.js`
user@sh$ export NODEJS_CONFIG
user@sh$ sh _devel_backend.sh

^ config is already exported in "$NODEJS_CONFIG"

^ running Node.JS backend
^ command: `node app_main/app_back.js`
^ ctlport: "3010"
.....
<<<< CTRL+D <<<<
Stop backend (y/n)?
ylftp_loop_done

[lftp->nodeJS:] sending 'cmd_exit'
ctl req url:/
ctl req url:/cmd_exit
$ MongoDB shutdown data: [Error: connection closed]
$db close: 127.0.0.1:27728
$ application is going down$ application exit with code: 0

$ backend process exit event

Normal Exit.
```

* lftp: add 'net:idle' and suffle options

Signed-off-by: Oleg Verych <olecom@gmail.com>