Fixups in libssl test harness

- select an actual file handle for devnull
- do not declare $msgdata twice
- SKE records sometimes seem to come without sig
- in SKE parsing, use and use $pub_key_len when parsing $pub_key

Reviewed-by: Matt Caswell <matt@openssl.org>

util/TLSProxy/Proxy.pm

@@ -142,7 +142,8 @@ sub start
     my $oldstdout;
 
     if(!$self->debug) {
-        $oldstdout = select(File::Spec->devnull());
+        open DEVNULL, ">", File::Spec->devnull();
+        $oldstdout = select(DEVNULL);
     }
 
     # Create the Proxy socket