Fix artifact cleanup

Author: chadlwilson

lib/context/docker_manifest_parser.rb

@@ -53,17 +53,17 @@ def select_image_info_at(position)
 
     def clean_artifacts
       Dir.children(@fldr).each do |name|
-        next if name == MANIFEST
-        File.delete "#{@fldr}/#{file}" if File.exist? "#{@fldr}/#{file}"
+        path = "#{@fldr}/#{name}"
+        File.delete path unless name == MANIFEST or !File.file? path
       end
     end
 
     private
 
     def clean_non_selected_artifacts
       Dir.children(@fldr).each do |name|
-        next if name == MANIFEST or name == @file
-        File.delete "#{@fldr}/#{file}" if File.exist? "#{@fldr}/#{file}"
+        path = "#{@fldr}/#{name}"
+        File.delete path unless name == MANIFEST or name == @file or !File.file? path
       end unless @file.nil?
     end