docker: add tests framework into Ubuntu16.04

"make check" command use cppunit and "sipp" for our tests framework.
Add them to our current validation docker file.
Also fix Acquire::Retries option (typo).

Change-Id: I92a1ad0b5aa3a8066c48445261ff38e4e5a01061
Reviewed-by: Olivier Soldano <olivier.soldano@savoirfairelinux.com>

docker/Dockerfile_ubuntu_16.04

 FROM ubuntu:16.04
 
 RUN apt-get update && \
-    apt-get install -y -o Acquire::Retires=10 \
+    apt-get install -y -o Acquire::Retries=10 \
         git \
         autoconf \
         automake \
@@ -55,4 +55,9 @@ RUN apt-get update && \
         libva-dev \
         libvdpau-dev
 
+# Tests framework
+RUN apt-get install -y -o Acquire::Retries=10 \
+        libcppunit-dev \
+        sip-tester
+
 RUN apt-get clean