Pin flintlock and containerd in e2e tests

[Callisto13]

something like:

-./flintlock/hack/scripts/provision.sh firecracker
+./flintlock/hack/scripts/provision.sh firecracker --version v0.25.2-macvtap

 # install and setup containerd
-curl -sL https://api.github.com/repos/containerd/containerd/releases/latest 2>/dev/null |
- jq -r '.assets[] | select(.browser_download_url | test("containerd-\\d.\\d.\\d-linux-amd64.tar.gz$")) | .browser_download_url' |
- xargs curl -sL | tar xz -C "$INSTALL_ROOT" && containerd --version && ctr --version
+
+curl -sL https://github.com/containerd/containerd/releases/download/v1.5.9/containerd-1.5.9-linux-amd64.tar.gz |
+ tar xz -C "$INSTALL_ROOT" && containerd --version && ctr --version

This is just while we get firecracker v1 working, and while we figure out what has changed with containerd.

Can be partly undone after #390