Instead of each subdir containing its own custom rule for checking the
augeas tests, use common rule for all.

The new rule searches both src + build dirs for include files, since
some augeas files will be auto-generated very shortly.
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>