net/handshake: Fix sock->file allocation

	sock->file = sock_alloc_file(sock, O_NONBLOCK, NULL);
	^^^^                         ^^^^

sock_alloc_file() calls release_sock() on error but the left hand
side of the assignment dereferences "sock".  This isn't the bug and
I didn't report this earlier because there is an assert that it
doesn't fail.

net/handshake/handshake-test.c:221 handshake_req_submit_test4() error: dereferencing freed memory 'sock'
net/handshake/handshake-test.c:233 handshake_req_submit_test4() warn: 'req' was already freed.
net/handshake/handshake-test.c:254 handshake_req_submit_test5() error: dereferencing freed memory 'sock'
net/handshake/handshake-test.c:290 handshake_req_submit_test6() error: dereferencing freed memory 'sock'
net/handshake/handshake-test.c:321 handshake_req_cancel_test1() error: dereferencing freed memory 'sock'
net/handshake/handshake-test.c:355 handshake_req_cancel_test2() error: dereferencing freed memory 'sock'
net/handshake/handshake-test.c:367 handshake_req_cancel...