Revert "vhost-user: Attempt to fix a race with set_mem_table."

This reverts commit 28ed5ef16384f12500abd3647973ee21b03cbe23.

I still think it's the right thing to do, but
tests have been failing sporadically.

Revert for now, and hope to fix it before the release.

Cc: Prerna Saxena <prerna.saxena@nutanix.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Marc-André Lureau <mlureau@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-id: 1471268075-3425-1-git-send-email-mst@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
