Add openolt protos to docker-based build.

Change-Id: Ie2e8b3c3ab9a8a4bf5d8e1a7d8889a4f087f74d5
diff --git a/docker/Dockerfile.base b/docker/Dockerfile.base
index a2dda2d..1b912e0 100644
--- a/docker/Dockerfile.base
+++ b/docker/Dockerfile.base
@@ -27,6 +27,7 @@
 RUN wget https://github.com/Yelp/dumb-init/releases/download/v1.2.0/dumb-init_1.2.0_amd64.deb && \
     dpkg -i *.deb && \
     rm -f *.deb && \
+    apt-get update && \
     apt-get install -y wget build-essential make gcc binutils python-dev libffi-dev libssl-dev git && \
     pip install -r /tmp/requirements.txt && \
     apt-get purge -y wget build-essential make gcc binutils python-dev libffi-dev libssl-dev git && \