metadata.json is parsed twice

When an instance of class Puppet::Module is created, the initialize method will first call has_metadata? to check if the metadata.json file is present and valid. This method will do a full parse of the file to check its validity. Next, the initializer will call the method load_metadata. It parses the same file once again.

Suggestion:

1. Add a validity check to the load_metadata method by adding a begin/rescue around its PSON.parse
2. Remove the call to has_metadata? from the initialize method