package/docker-containerd: add missing dependency on host-pkgconf

package/docker-containerd: add missing dependency on host-pkgconf

When libsseccomp support is enabled, docker-containerd uses pkg-config
to find libsseccomp, so we must depend on host-pkconf.

Fixes the following build issue, detected with per-package directory
support:

pkg-config: exec: "pkg-config": executable file not found in $PATH

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Christian Stewart <christian@paral.in>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>