The first call to query the mtu in dtls1_do_write correctly checks that the

The first call to query the mtu in dtls1_do_write correctly checks that the
mtu that we have received is not less than the minimum. If its less it uses the
minimum instead. The second call to query the mtu does not do that, but
instead uses whatever comes back. We have seen an instance in RT#3592 where we
have got an unreasonably small mtu come back. This commit makes both query
checks consistent.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 6abb0d1f8e702a0daa9c32b8021d01eda0483018)