Use containerd at HEAD until better tagged version is available.

Go 1.11.3 has a bug:
golang/go#29241

This is fixed/workarounded in containerd:
containerd/containerd@52de371

Until that commit has made it into a tagged version, we will use containerd at
head.

PiperOrigin-RevId: 225636987
Change-Id: I7e32beb7751f566f5b41682a29a14442c1aa56c2

kokoro/run_tests.sh

@@ -65,7 +65,10 @@ installCrictl() (
   # go get will exit with a status of 1 despite succeeding, so ignore errors.
   go get -d github.com/containerd/containerd || true
   cd ${GOPATH}/src/github.com/containerd/containerd
-  git checkout tags/v1.1.4
+  # TODO: Switch to using a tagged version once one has been cut
+  # that contains fix in:
+  # https://github.com/containerd/containerd/commit/52de3717005eb20141c305bd93ff0d6ee5dfecb6
+  git checkout master
   make
   sudo -n -E make install