rcutorture: Handle non-statistic bang-string error messages

The current console parsing assumes that console lines containing "!!!"
are statistics lines from which it can parse the number of rcutorture
too-short grace-period failures.  This prints confusing output for
other problems, including memory exhaustion.  This commit therefore
differentiates between these cases and prints an appropriate error string.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/parse-console.sh

@@ -44,11 +44,23 @@ then
 		tail -1 |
 		awk '
 		{
-			for (i=NF-8;i<=NF;i++)
+			normalexit = 1;
+			for (i=NF-8;i<=NF;i++) {
+				if (i <= 0 || i !~ /^[0-9]*$/) {
+					bangstring = $0;
+					gsub(/^\[[^]]*] /, "", bangstring);
+					print bangstring;
+					normalexit = 0;
+					exit 0;
+				}
 				sum+=$i;
 			}
-		END { print sum }'`
-		print_bug $title FAILURE, $nerrs instances
+		}
+		END {
+			if (normalexit)
+				print sum " instances"
+		}'`
+		print_bug $title FAILURE, $nerrs
 		exit
 	fi