Tests: adjusted resolver TODO, fix committed.

mail_resolver.t

diff --git a/mail_resolver.t b/mail_resolver.t
index 19b9c6b..0c5c11b 100644
--- a/mail_resolver.t
+++ b/mail_resolver.t
@@ -160,7 +160,7 @@
 # PTR with zero length RDATA
 
 TODO: {
-local $TODO = 'not yet';
+local $TODO = 'not yet' unless $t->has_version('1.5.8');
 
 $s = Test::Nginx::SMTP->new(PeerAddr => "127.0.0.1:8028");
 $s->read();