provision: RODC revision level should be at 2

provision: RODC revision level should be at 2

This number had been mistakenly updated alongside the standard forest
updates revision. This version number appears to be independent of the
other revision levels.

Also add the change to a new .ldf file, which can be used to apply
the schema change to an existing Samba 4.7 (or earlier) instance.
Update the provision/upgrade test to do just this (otherwise it
complains about differences between a new provision and an older Samba
4.0.0 instance).

Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>