[ruby/resolv] Catch EPROTONOSUPPORT as a sign of no IPv6 as well

(https://github.com/ruby/resolv/pull/41)

If IPv6 is disabled inside a freebsd jail, it seems this returns
EPROTONOSUPPORT and not EAFNOSUPPORT. In both cases, we should simply
try some other listed DNS servers.

Fixes [Bug #19928] https://bugs.ruby-lang.org/issues/19928

https://github.com/ruby/resolv/commit/5e2d48708b

lib/resolv.rb

@@ -750,7 +750,7 @@ class Resolv
               next if @socks_hash[bind_host]
               begin
                 sock = UDPSocket.new(af)
-              rescue Errno::EAFNOSUPPORT
+              rescue Errno::EAFNOSUPPORT, Errno::EPROTONOSUPPORT
                 next # The kernel doesn't support the address family.
               end
               @socks << sock