specs: Remove the @PREFIX@ substitution

Instead of rewriting the %setup directive in the spec file, we either
create a source tarball that adheres to RPM's conventions, producing a
directory called %{name}-%{version} when unpacked, or we override the
name using the '-n' flag in the %setup directive.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
specs: Remove conf.json

The information in this file has now been merged into the spec files.

Signed-off-by: Euan Harris <euan.harris@citrix.com>