tests/test-filter-redirector: move close()

tests/test-filter-redirector: move close()

Since we have separate handler on POLLHUP, which drops data
after closing the connection we need to fix this test, because
it sends data and instantly close the socket creating race condition.
In some cases on other end of socket client closes it faster than
reads data. To prevent it I suggest to close socket after recieving.

Signed-off-by: Klim Kireev <klim.kireev@virtuozzo.com>
Message-Id: <20180201134831.17709-1-klim.kireev@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>