containerd: provide 'ctr' along with 'containerd-ctr'

Historically we copied ctr into the install as containerd-ctr, but many
different guides expect 'ctr' to be present. So we make the copy and
then create a symlink to make both variants available.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

recipes-containers/containerd/containerd.inc

@@ -88,6 +88,8 @@ do_install() {
 	ln -sf containerd-shim ${D}/${bindir}/docker-containerd-shim
 	ln -sf containerd-ctr ${D}/${bindir}/docker-containerd-ctr
 
+	ln -sf containerd-ctr ${D}/${bindir}/ctr
+
 	if ${@bb.utils.contains('DISTRO_FEATURES','systemd','true','false',d)}; then
 		install -d ${D}${systemd_unitdir}/system
 		install -m 644 ${WORKDIR}/containerd.service ${D}/${systemd_unitdir}/system