fix: move docker data dir to /mnt to address e2e test low disk space for clean backport (#1220)

(cherry picked from commit 0b60f33e0de15293c1c06ab550b0a824c3b920aa)
Signed-off-by: Wei Weng <Wei.Weng@microsoft.com>

Author: Wei Weng

.github/workflows/ci.yml

@@ -41,7 +41,7 @@ jobs:
 
       - name: Check out code into the Go module directory
         uses: actions/checkout@v5
-              
+
       - name: Set up Ginkgo CLI
         run: |
           go install github.com/onsi/ginkgo/v2/ginkgo@v2.19.1
@@ -92,6 +92,25 @@ jobs:
       - name: Check out code into the Go module directory
         uses: actions/checkout@v5
 
+      - name: Move Docker data directory to /mnt
+        # The default storage device on GitHub-hosted runners is running low during e2e tests.
+        # Moving Docker data directory to /mnt which has more space and is backed by a larger
+        # storage device.
+        # Upstream kubefleet repo has a much bigger default storage device and no secondary
+        # storage device to use.
+        run: |
+          echo "=== Moving Docker to /mnt for more disk space ==="
+          df -h
+          sudo systemctl stop docker
+          echo '{"data-root": "/mnt/docker"}' | sudo tee /etc/docker/daemon.json
+          sudo mkdir -p /mnt/docker
+          if [ -d "/var/lib/docker" ]; then
+            sudo mv /var/lib/docker/* /mnt/docker/ || true
+          fi
+          sudo systemctl start docker
+          echo "=== Docker moved to /mnt, verifying ==="
+          docker info | grep "Docker Root Dir" || true
+
       - name: Install Ginkgo CLI
         run: |
           go install github.com/onsi/ginkgo/v2/ginkgo@v2.23.4