Repin NNG refs to capture proxy reconnect fix

A fix to address NNG issues when reconnecting a session
through a proxy was made on August 9, 2019 and merged into
the NNG master branch with commit ID e618abf8f3db2a9. This
change repins the references to the NNG repo such that the
fix is incorporated in the NNG library.

Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: I84d707b6ac65af8e7d78fa6814208532603ea177
diff --git a/docker/bldr-alpine3/Dockerfile b/docker/bldr-alpine3/Dockerfile
index 6b0fd3d..499e167 100644
--- a/docker/bldr-alpine3/Dockerfile
+++ b/docker/bldr-alpine3/Dockerfile
@@ -50,10 +50,13 @@
     && cp /tmp/autoconf-archive/m4/* /usr/share/aclocal \
     && rm -rf /tmp/autoconf-archive
 
-# NNG, version is pinned
+# NNG repo is not frequently tagged so it's pinned to a commit hash.
+# This commit provides fix to the proxy-reconnect
+# bug that we identified:  https://github.com/nanomsg/nng/issues/970
 RUN cd /tmp \
-    && git clone --branch v1.1.1 https://github.com/nanomsg/nng.git \
+    && git clone https://github.com/nanomsg/nng.git \
     && cd nng \
+    && git checkout e618abf8f3db2a94269a79c8901a51148d48fcc2 \
     && mkdir build \
     && cd build \
     && cmake -DBUILD_SHARED_LIBS=1 -G Ninja .. \
diff --git a/docker/bldr-alpine3/container-tag.yaml b/docker/bldr-alpine3/container-tag.yaml
index c51d3ac..d6ac6d8 100644
--- a/docker/bldr-alpine3/container-tag.yaml
+++ b/docker/bldr-alpine3/container-tag.yaml
@@ -1,4 +1,4 @@
 # Not feasible to show all the software versions
 # here so just use a counter plus the base image
 ---
-tag: 5-a3.9
+tag: 6-a3.9-nng