Fix broken certificate chain

In base Ubuntu image? Without this recent Let's Encrypt certs are not
accepted

Dockerfile

@@ -2,7 +2,10 @@ FROM        haffmans/cmake-qt5:latest
 MAINTAINER  Wouter Haffmans <wouter@simply-life.net>
 
 WORKDIR /
-RUN wget "https://git.simply-life.net/packages/ubuntu/xenial/qommando-master.tar.bz2" -O /tmp/qommando-master.tar.bz2 \
+# Disable mozilla/DST_Root_CA_X3.crt - it interferes with the newer Let's Encrypt certificates
+RUN    sed -i 's@mozilla/DST_Root_CA_X3.crt@!mozilla/DST_Root_CA_X3.crt@' /etc/ca-certificates.conf \
+    && update-ca-certificates \
+    && wget "https://git.simply-life.net/packages/ubuntu/xenial/qommando-master.tar.bz2" -O /tmp/qommando-master.tar.bz2 \
     && tar -jxvf /tmp/qommando-master.tar.bz2 \
     && rm /tmp/qommando-master.tar.bz2