only do hotplug2 init if hotplug2 is present

The current /init script unconditionally does the initialisation for
hotplug2, including mounting a new /dev. If hotplug2 isn't present, we
end up with no device nodes.

This change only does the hotplug2 init if hotplug2 is present, but
always mounts /sys.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

SVN-Revision: 9411