btrfs-progs: tests: add matching line for extent leaks to scan-results

The extent leaks are detected in debug builds but tests/scan-build.sh
does not look for them, so add the match expression.

Signed-off-by: David Sterba <dsterba@suse.com>

tests/scan-results.sh

@@ -14,6 +14,7 @@ for i in *.txt; do
 			*LeakSanitizer:*leak*) echo "SANITIZER REPORT: memory leak: $last" ;;
 			*Warning:\ assertion*failed*) echo "ASSERTION WARNING: $last" ;;
 			*command\ not\ found*) echo "COMMAND NOT FOUND: $last" ;;
+			*extent\ buffer\ leak*) echo "EXTENT BUFFER LEAK: $last" ;;
 			*) : ;;
 		esac
 	done < "$i"