fix: wait for async P2P send before deallocating output tensor#4047

ericharper merged 2 commits intoNVIDIA:mainNVIDIA/Megatron-LM:mainfrom

ZhiyuLi-Nvidia:zhiyul/fix/p2p-dealloc-raceZhiyuLi-Nvidia/Megatron-LM:zhiyul/fix/p2p-dealloc-raceCopy head branch name to clipboard