* lib/resolv.rb: fall back if canonicalization fails.
  Thanks Vit Ondruch for the patch!  [ruby-core:65836]

* test/resolv/test_dns.rb: test for patch

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e