[ruby/uri] Check if DN exists

	https://bugs.ruby-lang.org/issues/16830

	https://github.com/ruby/uri/commit/b4bf8c1217
	---
	 lib/uri/ldap.rb       | 1 +
	 test/uri/test_ldap.rb | 4 ++++
	 2 files changed, 5 insertions(+)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67914 b2dd03c8-39d4-4d8f-98ff-823fe69b080e