Revert "test_cdf_const: deactivated (depends on app/cdi)"

This reverts commit 584cabb1.

* We do this at least temporarily to monitor that the test works.

tests/Makefile.am

@@ -17,11 +17,9 @@ TESTS = cksum_verify \
 	pio_cksum_mpi_fw_at_all \
 	pio_cksum_mpi_fw_at_reblock \
 	test_resource_copy_run pio_write_deco2d_run \
-	test_f2003 test_cdf_transformation \
+	test_f2003 test_cdf_transformation test_cdf_const \
 	test_table_run test_byteswap_run
 
-#test_cdf_const: deactivated (depends on app/cdi)
-
 check_PROGRAMS = cksum_verify test_grib cksum_write cksum_read \
 	calendar_test1 \
 	test_month_adjust \