Added set_db_type function to set global debug symbol removed when

Added set_db_type function to set global debug symbol removed when
doing class based catalog backends. Coding is a bit different
as we need get_db_type which needs a bdb class so we have to
set it as part of the loop over all catalogs. This way we may
set the global variable a couple of times but the code frees
the global variable if needed so other then being somewhat overkill
no harm is done.