Fix wrong package name in Ubuntu Dockerfile

This corresponds to the change in the install instructions for Ubuntu
outlined in #335.

docker/Dockerfile.ubuntu

@@ -9,7 +9,7 @@ RUN apt-get update && apt-get install -y \
     libelf-dev \
     llvm-5.0-dev \
     zlib1g-dev \
-    bcc-dev
+    libbpfcc-dev
 
 COPY build.sh /build.sh
 ENTRYPOINT ["bash", "/build.sh"]