UBUNTU: cleanup conditional dependancy handling

BugLink: http://bugs.launchpad.net/bugs/603087

We commonly use conditional elements to limit building to specific
sub-systems.  Move to a new model wherein the variables are used directly
in the assignment so that enabled things are placed on foo-true and
disabled things go to foo-false.  Overall simplifying the code.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>