improve error messages in mindist

cmr=v1.7.4:reviewer=ompi-rm1.7

This commit was SVN r29846.

orte/mca/rmaps/mindist/help-orte-rmaps-md.txt

@@ -24,14 +24,20 @@ specifying multiple applications, you must specify how many processes
 of each to launch via the -np argument.
 #
 [orte-rmaps-mindist:no-pci-locality-info]
-No PCI locality information could be found on at least one node. Please, upgrade BIOS to expose NUMA info.
+No PCI locality information could be found on at least one node. 
+Please, upgrade BIOS to expose NUMA info.
 
   Node: %s
 
 Open MPI will map the application by default (BYSLOT).
 #
 [orte-rmaps-mindist:several-hca-devices]
-There are several OpenFabrics devices found on at least one node. To use rmaps_mindist mapper, please, specify the definite one.
+On at least one node, more than one OpenFabrics device was discovered. 
+In this scenario, passing the 'auto' option to the rmaps minimum 
+distance mapper is ambiguous and therefore not valid. 
+Please select the particular OpenFabrics device that you would like 
+to be mapped nearest via -mca rmaps_base_mapping_policy dist:<device>
+or --map-by dist:<device>, e.g. --map-by dist:mlx4_0.
 
   Devices: %d
   Node: %s