automation: Remove expired root certificates used to be used by let's encrypt

While the Let's Encrypt root certificate ISRG_Root_X1.crt is already
present, openssl seems to still check for the root certificate
DST_Root_CA_X3.crt which has expired. This prevent https connections.

Removing DST_Root_CA_X3 fix the issue.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

automation/build/ubuntu/trusty.dockerfile

@@ -47,3 +47,8 @@ RUN apt-get update && \
         apt-get autoremove -y && \
         apt-get clean && \
         rm -rf /var/lib/apt/lists* /tmp/* /var/tmp/*
+
+# Remove expired certificate that Let's Encrypt certificates used to relie on.
+# (Not needed anymore)
+RUN sed -i 's#mozilla/DST_Root_CA_X3\.crt#!\0#' /etc/ca-certificates.conf && \
+    update-ca-certificates