Fix a bug noted by Gus Correa on the user's list: mpi_paffinity_alone

appeared multiple times in ompi_info output (so did others, but this
is the one that was noticed).  Ensure that we don't repeat
opal_paffinity_base_register_params() multiple times.

This commit was SVN r24569.

opal/mca/paffinity/base/paffinity_base_open.c

@@ -53,6 +53,13 @@ char *opal_paffinity_base_applied_binding;
 int opal_paffinity_base_register_params(void)
 {
     int value, id;
+    static int been_here = 0;
+
+    /* We may get called twice; be harmless in that case. */
+    if (1 == been_here) {
+        return OPAL_SUCCESS;
+    }
+    been_here = 1;
 
     /* Debugging / verbose output */