src/runtime/virtcontainers/hook/mock contains a simple example hook in Go.
The only thing this is used for is for some tests in
src/runtime/pkg/katautils/hook_test.go. It doesn't really have anything
to do with the rest of the virtcontainers package.
So, move it next to the test code that uses it.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>