build-unit-test-docker: Add python-jsonschema

This package is used to validate JSON files against a
schema file, which will be useful for a few repositories
to do during tests.

Change-Id: I4e440617ec8d5dc5ba21c40ca51038166a92ef92
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 497f540..a46c1e1 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -189,6 +189,7 @@
     python-pip \
     python-setuptools \
     python-socks \
+    python-jsonschema \
     python3 \
     python3-dev\
     python3-yaml \