Ensure observabilitySRE image is pushed on DRA staging (#17569)

The `artifactDockerObservabilitySRE` gradle task *always* produces a tag with a
`SNAPSHOT` postfix. In the staging pipeline we use the shared
`qualified-version` script for determining the LS version. That script correctly
handles conditionally adding a `SNAPSHOT` postfix which is important for the
tagging scheme for pushing to our container registry. Given the intermediate tag
produced by the gradle task is never pushed anywhere we can update the build
script to ensure the "local" artifact is always referenced with the `SNAPSHOT`
postfix.

Author: donoghuc

.buildkite/scripts/dra/build-and-push-observability-sre.sh

@@ -17,7 +17,12 @@ echo "Pushing ObservabilitySRE container to Docker repository"
 docker_login
 
 # Get qualified version without SHA (this is what the gradle task will produce)
+# Note that the gradle task always produces a version with -SNAPSHOT so if the
+# workflow type is staging we need to append -SNAPSHOT to the version.
 QUALIFIED_VERSION="$(.buildkite/scripts/common/qualified-version.sh)"
+if [[ "${WORKFLOW_TYPE:-}" == "staging" && "${QUALIFIED_VERSION}" != *-SNAPSHOT ]]; then
+  QUALIFIED_VERSION="${QUALIFIED_VERSION}-SNAPSHOT"
+fi
 
 # Set environment variable to include SHA and get version with SHA
 QUALIFIED_VERSION_WITH_SHA="$(INCLUDE_COMMIT_ID=1 .buildkite/scripts/common/qualified-version.sh)"