Test suite: Listen on IPv6 and IPv4 loopback by default
Distributions handle host names for loopback addresses and their
resolution differently, which caused trouble with the previous
defaults of TEST_HOST=localhost and TEST_IP=[::1]. While they work
fine on Debian, tests on Ubuntu failed apparently randomly because
connections to localhost sometimes used 127.0.0.1, and setting
TEST_IP=127.0.0.1 would sometimes be hit by the opposite effect.
The best solution seems to be to let the test servers listen on both
IPv4 and IPv6 loopback addresses (127.0.0.1 and [::1]): "localhost"
should always resolve to at least one of them, so we don't have to
care about the details. Apache handles the transport layer anyway, so
this change will not hide bugs in mod_gnutls itself.
Listening on both addresses is achieved by treating TEST_IP as a list
of addresses to listen on, changing the default to "[::1] 127.0.0.1",
and building a config file containing "Listen" directives for the test
servers from that. With this change there is no need to export TEST_IP
to the test environment any more.
Users who want to set their own TEST_IP can do so as before, but
should note that IPv6 addresses must be enclosed in square brackets.
