Automatically cache expected IPs for t_client.sh on the first run

Automatically cache expected IPs for t_client.sh on the first run

Previously one had to manually define correct values for the
EXPECT_IFCONFIG* variables based on what IPv4 and IPv6 addresses
the test VPN server handed out.

This was a tedious process especially with large number of tests,
as the IPs changed for every test client and for every test. With this
patch t_client.sh figures out the correct IP addresses using an
--up script and caches them to a separate file for later use.

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1475491887-740-1-git-send-email-samuli@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg12587.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit df0b00c253e41cce9567be79dbd3faa14c60473b)