Fix AllSocketPairTest for open source.
Fix AllSocketPairTest for open source.

Setting timeouts for sockets on GCP images (debian) for usecs only
respects multiples of 4K. Set the test with a multiple of 4K with a comment.

PiperOrigin-RevId: 327093848

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor