waf: don't auto-depend on subsystems

waf: don't auto-depend on subsystems

this is part of an effort to reduce the amount of automatic dependency
munging we do. When working on the correct dependency tree for Samba
it is easier to add the right dependencies in the wscript files than
rely on them being added by the waf rules. This change removes the
automatic dependency of modules on their subsystem. Many modules don't
actually need this dependency anyway, so it is better to add it where
they are needed (for example, for ldb modules)

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>