Fix reconnect issues when --push and UDP is used on the server

Fix reconnect issues when --push and UDP is used on the server

When the server is configured with UDP and --push statements, reconnecting
often fails by the client never receiving PUSH_REPLY.  The client sends
PUSH_REQUEST and the server logs these requests but does not send them.

This bug got introduced in commit ff65da3a230b658b2c1d52dc1a48612e80a2eb42
which tries to avoid sending duplicated PUSH messages if the client/server
connection is slow.

This patch keeps this behaviour, but instead of a session wide PUSH_REPLY
block it sets an expiry time for the PUSH_REPLY block.  The expiry time
is set to 30 seconds.

Signed-off-by: David Sommerseth <davids@redhat.com>
Cc: James Yonan <james@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Acked-by: James Yonan <james@openvpn.net>
Message-Id: 1347154246-20143-1-git-send-email-dazo@users.sourceforge.net
URL: http://article.gmane.org/gmane.network.openvpn.devel/7044