ci: improve docker readiness and isolate dind cache per build pod

Jenkinsfile

@@ -57,8 +57,7 @@ spec:
     - name: docker-config-writable
       emptyDir: {}
     - name: dind-storage
-      persistentVolumeClaim:
-        claimName: jenkins-dind-cache
+      emptyDir: {}
     - name: harbor-config
       secret:
         secretName: harbor-bstein-robot
@@ -144,15 +143,25 @@ spec:
         container('builder') {
           sh '''
             set -euo pipefail
+            ready=0
             for i in $(seq 1 10); do
               if docker info >/dev/null 2>&1; then
+                ready=1
                 break
               fi
               sleep 2
             done
-            docker buildx create --name bstein-builder --driver docker-container \
+            if [ "${ready}" -ne 1 ]; then
+              echo "docker daemon did not become ready on ${DOCKER_HOST}" >&2
+              docker version || true
+              exit 1
+            fi
+            BUILDER_NAME="bstein-builder-${BUILD_NUMBER}"
+            docker buildx rm "${BUILDER_NAME}" >/dev/null 2>&1 || true
+            docker buildx create --name "${BUILDER_NAME}" --driver docker-container \
               --driver-opt image=moby/buildkit:buildx-stable-1 \
-              --bootstrap --use || docker buildx use bstein-builder
+              --bootstrap --use
+            docker buildx inspect "${BUILDER_NAME}" --bootstrap
           '''
         }
       }