Any update on this issue? 26min is too much 
$time /usr/share/kibana/bin/kibana-plugin install x-pack
Found previous install attempt. Deleting...
Attempting to transfer from x-pack
Attempting to transfer from https://artifacts.elastic.co/downloads/kibana-plugins/x-pack/x-pack-6.1.1.zip
Transferring 269804609 bytes....................
Transfer complete
Retrieving metadata from plugin archive
Extracting plugin archive
Extraction complete
Optimizing and caching browser bundles...
Plugin installation complete
real 26m8.734s
user 26m13.996s