TT#60950 Switch sipwise-base docker to buster

Change-Id: I23a5347bdcc29eaec5c8801f1d347a08cb37f25a

t/Dockerfile

@@ -1,11 +1,11 @@
-# DOCKER_NAME=sipwise-base-stretch
-FROM docker.mgm.sipwise.com/sipwise-stretch:latest
+# DOCKER_NAME=sipwise-base-buster
+FROM docker.mgm.sipwise.com/sipwise-buster:latest
 
 # Important! Update this no-op ENV variable when this Dockerfile
 # is updated with the current date. It will force refresh of all
 # of the base images and things like `apt-get update` won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT 2018-01-13
+ENV REFRESHED_AT 2019-06-27
 
 RUN apt-get update && apt-get install --assume-yes libmodule-build-perl libtrycatch-perl libstrictures-perl
 
@@ -20,13 +20,13 @@ WORKDIR /code/
 # (jump to the next section if you don't want to build yourself!):
 #
 # NOTE: run the following command from root folder of git repository:
-# % docker build --tag="sipwise-base-stretch" -f ./t/Dockerfile .
-# % docker run --rm -i -t -v $(pwd):/code:rw sipwise-base-stretch:latest bash
+# % docker build --tag="sipwise-base-buster" -f ./t/Dockerfile .
+# % docker run --rm -i -t -v $(pwd):/code:rw sipwise-base-buster:latest bash
 #
 # Use the existing docker image:
-# % docker pull docker.mgm.sipwise.com/sipwise-base-stretch
+# % docker pull docker.mgm.sipwise.com/sipwise-base-buster
 # NOTE: run the following command from root folder of git repository:
-# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/sipwise-base-stretch:latest bash
+# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/sipwise-base-buster:latest bash
 #
 # Inside docker:
 #   cd /code && ./t/testrunner