Tweak output of "srun --mpi=list"

Try to downplay the explicitly pmix versions - generally users should just
run with "pmix", and ignore the explicit version number.

NEWS

@@ -28,6 +28,7 @@ documents those changes that are of interest to users and administrators.
  -- Use accept4() and pipe2() to ensure new file descriptors are always set
     with close-on-exec flag.
  -- slurmctld - allow users to request tokens for themselves by name.
+ -- srun - adjust output of "--mpi=list".
 * Changes in Slurm 22.05.0rc1
 =============================

src/common/plugrack.c

@@ -403,12 +403,12 @@ extern int plugrack_print_mpi_plugins(plugrack_t *rack)
 {
 	ListIterator itr;
 	plugrack_entry_t *e = NULL;
-	char *sep, tmp[64];
+	char *sep, tmp[64], *pmix_vers = NULL, *comma = "";
 	int i;
 
 	xassert(rack->entries);
 	itr = list_iterator_create(rack->entries);
-	info("MPI types are...");
+	printf("MPI plugin types are...\n");
 	while ((e = list_next(itr))) {
 		/*
 		 * Support symbolic links for various pmix plugins with names
@@ -424,12 +424,22 @@ extern int plugrack_print_mpi_plugins(plugrack_t *rack)
 			if (sep)
 				sep[0] = '\0';
 			sep = tmp;
+
+			if (!xstrncmp(sep, "pmix_", 5)) {
+				xstrfmtcat(pmix_vers, "%s%s", comma, sep);
+				comma = ",";
+				continue;
+			}
 		} else
 			sep = (char *) e->full_type;	/* Remove "const" */
-		info("%s", sep);
+		printf("\t%s\n", sep);
 	}
 	list_iterator_destroy(itr);
 
+	if (pmix_vers)
+		printf("specific pmix plugin versions available: %s\n", pmix_vers);
+	xfree(pmix_vers);
+
 	return SLURM_SUCCESS;
 }