Add test for reopening socketpair end via procfs.
Add test for reopening socketpair end via procfs.

PiperOrigin-RevId: 227738801
Change-Id: Ic0c5d10c3b1f21b3f85ff9a661a55db77fab77b0

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