Bump s2n commit in Dockerfile

This bumps the `s2n` commit to
GaloisInc/s2n@7f1017e, which points to the
`llvm_points_to_bitfield` changes that were merged into the upstream `s2n-tls`
repo in aws/s2n-tls#3155.

s2nTests/docker/s2n.dockerfile

@@ -11,6 +11,7 @@ RUN apt-get update -y -q && \
     llvm-3.9 \
     make \
     sudo \
+    wget \
     && \
     rm -rf /var/lib/apt/lists/*
 
@@ -19,10 +20,10 @@ RUN mkdir -p /saw-script && \
     git clone https://github.com/GaloisInc/s2n.git && \
     mkdir -p s2n/test-deps/saw/bin && \
     cd s2n && \
-    git checkout 6586f1ad3b35efcd2287ab98a4be124449dcb780
+    git checkout 7f1017ee9b09ab6910f1d2bf56135663ca0b12c5
 
 
 
 COPY scripts/s2n-entrypoint.sh /entrypoint.sh
 ENTRYPOINT [ "/entrypoint.sh" ]
-CMD [ "/bin/bash" ]
+CMD [ "/bin/bash" ]