New NO_DEVICE_DISCOVERY option to replace WEAK_AUTHORITY option

The option disables device enumeration (and hotplug, which depends on
enumeration). Since this has a much broader usage scope than "weak
authority", give the option a name reflecting what it does.

For now, keep the old option name working as an alias.

Closes #935

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>
Signed-off-by: Nathan Hjelm <hjelmn@google.com>