Plugin installation: also create the id file for source plugins (#647)
Plugin installation: also create the id file for source plugins (#647)

For consistency, create the id file for all plugins.

I intend to use this file as a "this is actually a plugin directory"
marker ("...a fully installed plugin, at that")

Co-authored-by: Łukasz Maksymczuk <6c5eb78e54fa6aff67ba440c4bd5b1e43956c922@lukasz-maksymczuk.intra.codilime.com>
cloudify-cosmo/cloudify-agent,cloudify-cosmo/cloudify-agent