tests: Update containerd test to v1.3.4
-FROM linuxkit/alpine:bc528cf9d4065d2e09aa44ff76909b94cfe8d867 AS mirror
+FROM linuxkit/alpine:e2391e0b164c57db9f6c4ae110ee84f766edc430 AS mirror
RUN mkdir -p /out/etc/apk && cp -r /etc/apk/* /out/etc/apk/
# btrfs-progfs is required for btrfs test (mkfs.btrfs)
# util-linux is required for btrfs test (losetup)
