tests/docker: Install SASL library to extend code coverage on amd64

Install the SASL library to build the VNC SASL auth protocol code.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200309122454.22551-3-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/docker/dockerfiles/debian-amd64.docker

@@ -17,6 +17,7 @@ RUN apt update && \
         libbz2-dev \
         liblzo2-dev \
         librdmacm-dev \
+        libsasl2-dev \
         libsnappy-dev \
         libvte-dev