jobs/osmo-gsm-tester virtual: fix docker img

Build the docker image right before using it, instead of building it in
another jenkins job update-osmo-ci-on-slaves via
osmo-ci-docker-rebuild.sh.

The logic in osmo-ci-docker-rebuild.sh was broken. I didn't realize at
the time that this image is only used for the virtual osmo-gsm-tester,
not the physical ones. But only the machines running the physical
osmo-gsm-tester have the /var/tmp/osmo-gsm-tester/state path. The
virtual osmo-gsm-tester isn't running on these machines but on generic
jenkins nodes.

Building the image right before using it makes sense for this job, as it
is the only user of the image. If it was already built from the same
Dockerfile, a cached version is used.

Fix for:
  Unable to find image 'osmocom-build/osmo-gsm-tester:latest' locally

Fixes: 9139e76b ("osmo-ci-docker-rebuild: don't always build osmo-gsm-tester")
Change-Id: Icad9459de1d3a3a4e65ecacf7f903433bb504cc9

jobs/osmo-gsm-tester-runner.yml

@@ -224,6 +224,16 @@
       - copy_artifact:
          repo: osmo-gsm-tester_build-osmocom-bb
       - shell: |
+            # Build the docker image
+            rm -rf docker-playground
+            git clone \
+              --depth=1 \
+              --branch="$DOCKER_PLAYGROUND_BRANCH" \
+              https://gerrit.osmocom.org/docker-playground \
+              docker-playground
+            git -C docker-playground log --oneline
+            make -C docker-playground/osmo-gsm-tester
+
             unlink osmo-gsm-tester/sysmocom/resources.conf || true
 
             ln -s resources.conf.virtual osmo-gsm-tester/sysmocom/resources.conf
@@ -260,3 +270,7 @@
           name: "OSMO_GSM_TESTER_BRANCH"
           default: "master"
           description: "Which branch/sha should be used for testing"
+      - string:
+          name: "DOCKER_PLAYGROUND_BRANCH"
+          default: "master"
+          description: "Which branch/sha should be used for building the osmo-gsm-tester docker container"

scripts/osmo-ci-docker-rebuild.sh

@@ -10,8 +10,3 @@ if [ "$(arch)" = "x86_64" ]; then
 		"debian-bullseye-erlang" \
 		"debian-bullseye-jenkins"
 fi
-
-if [ -d "/var/tmp/osmo-gsm-tester/state" ]; then
-	docker_images_require \
-		"osmo-gsm-tester"
-fi