Dial it back a bit

Signed-off-by: Clinton Wolfe <clintoncwolfe@gmail.com>

lib/train.rb

@@ -62,8 +62,9 @@ def self.load_transport(transport_name)
   end
 
   # Legacy code to unpack a series of items from an incoming Hash
-  # Inspec::Config.unpack_train_credentials now handles this in most cases
-  def self.target_config(config) # TODO: deprecate
+  # Inspec::Config.unpack_train_credentials now handles this in most cases that InSpec needs
+  # If you need to unpack a URI, use upack_target_from_uri
+  def self.target_config(config = nil)
     conf = config.dup
     # Symbolize keys
     conf.keys.each do |key|
@@ -100,7 +101,8 @@ def self.unpack_target_from_uri(uri_string, opts = {}) # rubocop: disable Metric
     # ensure path is nil, if its empty; e.g. required to reset defaults for winrm # TODO: move logic into winrm plugin
     creds[:path] = nil if !creds[:path].nil? && creds[:path].to_s.empty?
 
-    creds.compact!
+    # compat! is available in ruby 2.4+
+    creds = creds.delete_if { |_, value| value.nil? }
 
     # return the updated config
     creds

lib/train/plugins/transport.rb

@@ -41,12 +41,6 @@ def self.name(name)
       Train::Plugins.registry[name] = self
     end
 
-    # Describe the defaults for the options this transport provides.
-    def self.credential_option_defaults
-      # TODO
-      {}
-    end
-
     private
 
     # @return [Logger] logger for reporting information