package/docker-containerd: security bump to 1.2.11

package/docker-containerd: security bump to 1.2.11

Fixes the following security vulnerabilities:

containerd 1.2.9/gRPC:

- CVE-2019-9512: Some HTTP/2 implementations are vulnerable to ping floods,
  potentially leading to a denial of service.  The attacker sends continual
  pings to an HTTP/2 peer, causing the peer to build an internal queue of
  responses.  Depending on how efficiently this data is queued, this can
  consume excess CPU, memory, or both

- CVE-2019-9514: Some HTTP/2 implementations are vulnerable to a reset
  flood, potentially leading to a denial of service.  The attacker opens a
  number of streams and sends an invalid request over each stream that
  should solicit a stream of RST_STREAM frames from the peer.  Depending on
  how the peer queues the RST_STREAM frames, this can consume excess memory,
  CPU, or both

- CVE-2019-9515: Some HTTP/2 implementations are vulnerable to a settings
  flood, potentially leading to a denial of service.  The attacker sends a
  stream of SETTINGS frames to the peer.  Since the RFC requires that the
  peer reply with one acknowledgement per SETTINGS frame, an empty SETTINGS
  frame is almost equivalent in behavior to a ping.  Depending on how
  efficiently this data is queued, this can consume excess CPU, memory, or
  both

containerd 1.2.10/runc:

- CVE-2019-16884: runc through 1.0.0-rc8, as used in Docker through
  19.03.2-ce and other products, allows AppArmor restriction bypass because
  libcontainer/rootfs_linux.go incorrectly checks mount targets, and thus a
  malicious Docker image can mount over a /proc director

Signed-off-by: Christian Stewart <christian@paral.in>
[Peter: mention security impact]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>