fcoll/base: do not use the two_phase compoment with CUDA support

the two_phase compoment does not work with some collective I/O
operations on CUDA buffers due to the data sieving (i.e.
both read and write operations) executed on some buffers, which are
not anticipated in the GPU buffer management of the code.

Signed-off-by: Edgar Gabriel <egabriel@central.uh.edu>

ompi/mca/fcoll/base/fcoll_base_file_select.c

@@ -280,11 +280,18 @@ int mca_fcoll_base_query_table (struct ompio_file_t *file, char *name)
         }
     }
     if (!strcmp (name, "two_phase")) {
+#if OPAL_CUDA_SUPPORT
+        /* do not use the two_phase component with CUDA
+           buffers, since the data sieving causes trouble 
+           on unmanaged GPU buffers.
+        */
+#else
         if ((int)file->f_cc_size < file->f_bytes_per_agg &&
             (0 == file->f_stripe_size || file->f_cc_size < file->f_stripe_size) && 
 	    (LUSTRE != file->f_fstype) ) {
             return 1;
         }
+#endif
     }
     return 0;
 }