Test failures on oflks333 due to missing bufr tables

[gerritholl]

Two tests are failing on oflks333 because bufr tables are missing. Those tables should be found by being included or the tests should mock whatever external is missing:

    def load_tab_b(tables, fname):
        """Load table B (elements) from 'fname' into object Tables."""
        if not os.path.exists(fname):
>           raise BufrTableError(_text_file_not_found % fname)
E           trollbufr.coder.errors.BufrTableError: BufrTableError: Table not found: '/media/x22264/nwcsaf/COTS/bufrtables/table_b_013'

that hardcoding isn't very useful.