2) kerberos authentication when canonicalize_host_name is true correctly authenticates when using the IP
     Failure/Error: ::URI.decode(value)
     
     NoMethodError:
       undefined method `gsub' for nil:NilClass
     # ./lib/mongo/uri.rb:404:in `decode'
     # ./lib/mongo/uri.rb:565:in `auth_source'
     # ./lib/mongo/uri.rb:491:in `apply_transform'
     # ./lib/mongo/uri.rb:545:in `add_uri_option'
     # ./lib/mongo/uri.rb:336:in `block in parse_uri_options!'
     # ./lib/mongo/uri.rb:329:in `each'
     # ./lib/mongo/uri.rb:329:in `reduce'
     # ./lib/mongo/uri.rb:329:in `parse_uri_options!'
     # ./lib/mongo/uri.rb:323:in `parse_db_opts!'
     # ./lib/mongo/uri.rb:303:in `parse!'
     # ./lib/mongo/uri.rb:258:in `initialize'
     # ./lib/mongo/uri.rb:219:in `new'
     # ./lib/mongo/uri.rb:219:in `get'
     # ./lib/mongo/client.rb:307:in `initialize'
     # ./spec/enterprise_auth/kerberos_spec.rb:25:in `new'
     # ./spec/enterprise_auth/kerberos_spec.rb:25:in `block (2 levels) in <top (required)>'
     # ./spec/enterprise_auth/kerberos_spec.rb:35:in `block (2 levels) in <top (required)>'
     # ./spec/enterprise_auth/kerberos_spec.rb:53:in `block (3 levels) in <top (required)>'