Re-enable CRIU tests by not using overlayfs snapshotter

While the issue hasn't been fixed in the kernel yet, we can workaround
the issue by not using overlayfs snapshotter.

The newly added step runs all tests that match /TestCheckpoint/.
So, TestCRWithImagePath has been renamed to match the regexp.

Fixes #3930.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

.github/workflows/ci.yml

@@ -322,6 +322,22 @@ jobs:
           sudo GOPATH=$GOPATH GOPROXY=$GOPROXY TEST_RUNTIME=$TEST_RUNTIME RUNC_FLAVOR=$RUNC_FLAVOR TESTFLAGS_PARALLEL=1 make integration EXTRA_TESTFLAGS=-no-criu
         working-directory: src/github.com/containerd/containerd
 
+      # CRIU wouldn't work with overlay snapshotter yet.
+      # See https://github.com/containerd/containerd/pull/4708#issuecomment-724322294.
+      - name: CRIU Integration
+        env:
+          GOPROXY: direct
+          TEST_RUNTIME: ${{ matrix.runtime }}
+          RUNC_FLAVOR: ${{ matrix.runc }}
+        # crun doesn't have "checkpoint" command.
+        if: ${{ matrix.runc == 'runc' }}
+        run: |
+          sudo GOPATH=$GOPATH GOPROXY=$GOPROXY \
+          TEST_RUNTIME=$TEST_RUNTIME RUNC_FLAVOR=$RUNC_FLAVOR TESTFLAGS_PARALLEL=1 \
+          TEST_SNAPSHOTTER=native \
+          make integration EXTRA_TESTFLAGS='-run TestCheckpoint'
+        working-directory: src/github.com/containerd/containerd
+
       - name: CRI Integration Test
         env:
           TEST_RUNTIME: ${{ matrix.runtime }}