fix plugin launcher SetConfig msgpack params (#6776)
fix plugin launcher SetConfig msgpack params (#6776)

* fix plugin launcher SetConfig msgpack params

The plugin launcher tool was passing the wrong byte array into
`SetConfig`, resulting in msgpack decoding errors. This was fixed in
a949050 (#6725) but accidentally reverted in 6aff18d (#6590).

Co-Authored-By: Chris Baker <aece4f852fbe8dfb010a6cf9f6cd824f140257e1@users.noreply.github.com>

dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,hashicorp/nomad,burdandrei/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,burdandrei/nomad,burdandrei/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad