REGTEST: ssl: test the client certificate authentication

This reg-test tests the client auth feature of HAProxy for both the
backend and frontend section with a CRL list.

This reg-test uses 2 chained listeners because vtest does not handle the
SSL. Test the frontend client auth and the backend side at the same
time.

It sends 3 requests: one with a correct certificate, one with an expired
one and one which was revoked. The client then checks if we received the
right one with the right error.

Certificates, CA and CRL are expiring in 2050 so it should be fine for
the CI.

This test could be backported as far as HAProxy 1.6
diff --git a/reg-tests/ssl/crl-auth.pem b/reg-tests/ssl/crl-auth.pem
new file mode 100644
index 0000000..af59d1d
--- /dev/null
+++ b/reg-tests/ssl/crl-auth.pem
@@ -0,0 +1,18 @@
+-----BEGIN X509 CRL-----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+-----END X509 CRL-----