EATTLE - The Celtics' frustration has reached a high level. That much was clear when Kenny Anderson vented about Boston's recent inconsistent play and said, ''This is [expletive].'' He was not referring specifically to the Celtics' 99-79 loss to the Sonics Saturday night, but rather to their up-and-down performances throughout the first four games of a seven-game road trip. Win. Loss. Win. Loss.