examples: pin version of go-control-plane (envoyproxy#17553) (envoyproxy#17683)

Re-ordered the operations from how it was done in envoyproxy#17553 to fix an error regarding the `git checkout` would lose local changes to `resource.go`.

Changed the pinned version to one from the 1.19 release.

Co-authored-by: Snow Pettersen <snowp@lyft.com>
(cherry picked from commit 38b6fd5, PR envoyproxy#17553)
Signed-off-by: Greg Greenway <ggreenway@apple.com>

Author: ggreenway

examples/dynamic-config-cp/Dockerfile-control-plane

@@ -6,7 +6,7 @@ RUN apt-get update \
     && apt-get clean \
     && rm -rf /tmp/* /var/tmp/* /var/lib/apt/lists/*
 
-RUN git clone https://github.com/envoyproxy/go-control-plane
+RUN git clone https://github.com/envoyproxy/go-control-plane && cd go-control-plane && git checkout b19e718c57df1835047cfae67798ac861eb8847e
 ADD ./resource.go /go/go-control-plane/internal/example/resource.go
 RUN cd go-control-plane && make bin/example
 WORKDIR /go/go-control-plane