Assign large blocks first in ADIOI_GPFS_Calc_file_domains

For files that are less than the size of a gpfs block there seems to be
an issue if successive MPI_File_write_at_all are called with proceeding
offsets.  Given the simple case of 2 aggs, the 2nd agg/fd will be utilized,
however the initial offset into the 2nd agg is distorted on the 2nd call
to MPI_File_write_at_all because of the negative size of the 1st agg/fd
because the offset info the 2nd agg/fd is influenced by the size of the
first.  Simple solution is to reverse the default large block assignment so
in the case where only 1 agg/fd will be used it will be the first.  By chance
in the 2 agg situation this is what the GPFSMPIO_BALANCECONTIG
optimization does and it does not have this problem.
Signed-off-by: Rob Latham <robl@mcs.anl.gov>

src/mpi/romio/adio/ad_gpfs/ad_gpfs_aggrs.c

@@ -367,10 +367,10 @@ void ADIOI_GPFS_Calc_file_domains(ADIO_File fd,
 	/* BG/L- and BG/P-style distribution of file domains: simple allocation of
 	 * file domins to each aggregator */
 	for (i=0; i<naggs; i++) {
-	    if (i < naggs_small) {
-		fd_size[i] = nb_cn_small     * blksize;
-	    } else {
+	    if (i < naggs_large) {
 		fd_size[i] = (nb_cn_small+1) * blksize;
+	    } else {
+		fd_size[i] = nb_cn_small     * blksize;
 	    }
 	}
     }
@@ -387,12 +387,12 @@ void ADIOI_GPFS_Calc_file_domains(ADIO_File fd,
 
 #else // not BGQ platform
 	for (i=0; i<naggs; i++) {
-	    if (i < naggs_small) {
-		fd_size[i] = nb_cn_small     * blksize;
-	    } else {
+	    if (i < naggs_large) {
 		fd_size[i] = (nb_cn_small+1) * blksize;
+	    } else {
+		fd_size[i] = nb_cn_small     * blksize;
 	    }
-	}
+    }
 
 #endif