Verify expectations better in SockDiagTest.

Currently SockDiagTest only checks for socket errors, it does not
check that the socket was closed via SOCK_DESTROY. This can cause
us to think that SOCK_DESTROY is working when it isn't.

Fix this by checking the error codes and expecting that at least
one socket was closed by SOCK_DESTROY.

Bug: 28508161

(cherry picked from commit 6bdc41f3)

Change-Id: I0e0368145247bfd0f946692381dcd78991811413