maintner/maintnerd: add grpc dep to Dockerfile

Change-Id: Ifeca2a552299d783b5447bab5fe5a48ea78a1a79
Reviewed-on: https://go-review.googlesource.com/43617
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/maintner/maintnerd/Dockerfile.0 b/maintner/maintnerd/Dockerfile.0
index 76b4cb2..068aae9 100644
--- a/maintner/maintnerd/Dockerfile.0
+++ b/maintner/maintnerd/Dockerfile.0
@@ -31,6 +31,9 @@
 RUN go get golang.org/x/crypto/acme/autocert && \
     cd /go/src/golang.org/x/crypto && git reset --hard c7af5bf2638a1164f2eb5467c39c6cffbd13a02e
 
+RUN go get go4.org/grpc && \
+    cd /go/src/go4.org/grpc && git reset --hard 32ab3eb96f50a8c0f4103aa8d149cd1f15576636
+
 # Optimization to speed COPY+go install steps later. This go install
 # isn't required for correctness.
 RUN go install golang.org/x/oauth2 \