TT#118659 Switch Dockerfile from Debian buster to bullseye

Change-Id: I32e93d62cd2a9669b88c1dfe719efcf5b0d11950

t/Dockerfile

@@ -1,11 +1,11 @@
-# DOCKER_NAME=kamailio-config-tests-buster
-FROM docker.mgm.sipwise.com/sipwise-buster:latest
+# DOCKER_NAME=kamailio-config-tests-bullseye
+FROM docker.mgm.sipwise.com/sipwise-bullseye: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 2019-10-15
+ENV REFRESHED_AT 2021-05-03
 
 # test execution; we need the backport of python3-junitxml from our own
 # repository since it's not part of Debian/buster
@@ -29,14 +29,14 @@ WORKDIR /code/
 #
 # you need to put the proper NGCP sources at t/sources.list.d/builddeps.list
 # for instance, trunk:
-# echo "deb https://deb.sipwise.com/autobuild/ release-trunk-buster main" > t/sources.list.d/builddeps.list
+# echo "deb https://deb.sipwise.com/autobuild/ release-trunk-bullseye main" > t/sources.list.d/builddeps.list
 #
-# % docker build --tag="kamailio-config-tests-buster" -f t//Dockerfile .
-# % docker run --rm -i -t -v $(pwd):/code:rw kamailio-config-tests-buster:latest bash
+# % docker build --tag="kamailio-config-tests-bullseye" -f t//Dockerfile .
+# % docker run --rm -i -t -v $(pwd):/code:rw kamailio-config-tests-bullseye:latest bash
 #
 # Use the existing docker image:
-# % docker pull docker.mgm.sipwise.com/kamailio-config-tests-buster
-# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/kamailio-config-tests-buster:latest bash
+# % docker pull docker.mgm.sipwise.com/kamailio-config-tests-bullseye
+# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/kamailio-config-tests-bullseye:latest bash
 #
 # Inside docker (the command is in history, just press UP button):
 #   ./t/testrunner