[8.14] [ci/docker] Only run commands if docker bin exists (#183310) (#…

…183324)

# Backport

This will backport the following commits from `main` to `8.14`:
- [[ci/docker] Only run commands if docker bin exists
(#183310)](#183310)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT
[{"author":{"name":"Jon","email":"jon@elastic.co"},"sourceCommit":{"committedDate":"2024-05-13T16:14:37Z","message":"[ci/docker]
Only run commands if docker bin exists (#183310)\n\nFixes specific
cases, like static agents used for updating caches\r\nwithout the docker
binary, from running docker
commands.","sha":"931b587dacb9f75c107248a7be70e5b78d91c249","branchLabelMapping":{"^v8.15.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["Team:Operations","release_note:skip","backport:prev-minor","v8.15.0"],"title":"[ci/docker]
Only run commands if docker bin
exists","number":183310,"url":"#183310
Only run commands if docker bin exists (#183310)\n\nFixes specific
cases, like static agents used for updating caches\r\nwithout the docker
binary, from running docker
commands.","sha":"931b587dacb9f75c107248a7be70e5b78d91c249"}},"sourceBranch":"main","suggestedTargetBranches":[],"targetPullRequestStates":[{"branch":"main","label":"v8.15.0","branchLabelMappingKey":"^v8.15.0$","isSourceBranch":true,"state":"MERGED","url":"#183310
Only run commands if docker bin exists (#183310)\n\nFixes specific
cases, like static agents used for updating caches\r\nwithout the docker
binary, from running docker
commands.","sha":"931b587dacb9f75c107248a7be70e5b78d91c249"}}]}]
BACKPORT-->

Co-authored-by: Jon <jon@elastic.co>

.buildkite/scripts/common/setup_job_env.sh

@@ -21,7 +21,9 @@ fi
 
   KIBANA_DOCKER_USERNAME="$(vault_get container-registry username)"
   KIBANA_DOCKER_PASSWORD="$(vault_get container-registry password)"
-  echo "$KIBANA_DOCKER_PASSWORD" | docker login -u "$KIBANA_DOCKER_USERNAME" --password-stdin docker.elastic.co
+  if command -v docker &> /dev/null; then
+    echo "$KIBANA_DOCKER_PASSWORD" | docker login -u "$KIBANA_DOCKER_USERNAME" --password-stdin docker.elastic.co
+  fi
 }
 
 # Set up a custom ES Snapshot Manifest if one has been specified for this build