cleanup-self-hosted-runner: clean up idle runners earlier

The original idea was to wait at least 3 hours before deleting a VM, to
avoid interfering with long-running workflows.

Now that we have a way to query whether the runner _is_ busy, we do not
need to wait that long. Basically, we only need to ensure that the
runner had a chance to register itself and to then pick up the job.
Typically, this takes around 6-7 minutes, so waiting for an hour is
probably even a tad conservative.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/cleanup-self-hosted-runners.yml

@@ -29,7 +29,7 @@ jobs:
         inlineScript: |
           active_vms=$(az vm list -g ${{ secrets.AZURE_RESOURCE_GROUP }} | jq -c '.[] | {name,timeCreated}')
           current_time=$(date +%s)
-          three_hours_ago=$(($current_time - 3 * 3600))
+          one_hour_ago=$(($current_time - 3600))
 
           if [ -z "$active_vms" ]; then
               echo "No active VMs found, nothing to do."
@@ -44,7 +44,7 @@ jobs:
               vm_creation_iso_string=$(echo $active_vm | jq -r '.timeCreated')
               vm_creation_time=$(date -d $vm_creation_iso_string +%s)
               
-              if [ "$three_hours_ago" -lt "$vm_creation_time" ]; then
+              if [ "$one_hour_ago" -lt "$vm_creation_time" ]; then
                   echo "The VM ${vm_name} was created less then 3 hours ago and shouldn't be deleted yet. Skipping."
               elif test true = "$(gh api repos/$GITHUB_REPOSITORY/actions/runners \
                   --jq '.runners[] | select(.name == "'$vm_name'") | .busy)"; then