Add websocket to pip3 install

Required for automated websocket test, which uses Python and Robot
Framework.

Signed-off-by: Michael Shepos <shepos@us.ibm.com>
Change-Id: I3eae6443943f11af8e2c78d4751fefa087ec87ea
diff --git a/scripts/build-qemu-robot-docker.sh b/scripts/build-qemu-robot-docker.sh
index 48c5203..3c195ab 100755
--- a/scripts/build-qemu-robot-docker.sh
+++ b/scripts/build-qemu-robot-docker.sh
@@ -71,6 +71,7 @@
     tox \
     requests \
     retrying \
+    websocket \
     json2yaml \
     robotframework \
     robotframework-requests \