FIX: Do not activate plugins before checking compatibility (#124)

discourse/discourse#15537

Author: davidtaylorhq

lib/docker_manager/upgrader.rb

@@ -92,7 +92,7 @@ def upgrade
 
     run("bundle install --deployment --jobs 4 --without test development")
     begin
-      run("bundle exec rake plugin:pull_compatible_all")
+      run("LOAD_PLUGINS=0 bundle exec rake plugin:pull_compatible_all")
     rescue RuntimeError
       log "Unable checkout compatible plugin versions"
     end