test: accept EPROTONOSUPPORT ipv6 error

The IPv6 test in parallel/test-dgram-error-message-address may fail
when the host system has disabled IPv6, as is the case on our FreeBSD
machines.  The test already accepted EAFNOSUPPORT as of commit 5ba307a9,
now make it accept EPROTONOSUPPORT as well.

I'm not exactly thrilled by the profusion of error codes but they are
all legitimate.

PR-URL: https://github.com/iojs/io.js/pull/733


Reviewed-By: Fedor Indutny <fedor@indutny.com>