vhost: propagate set features handling error

vhost: propagate set features handling error

Not propagating VHOST_USER_SET_FEATURES request handling
error may result in unpredictable behavior, as host and
guests features may no more be synchronized.

This patch fixes this by reporting the error to the upper
layer, which would result in the device being destroyed
and the connection with the master to be closed.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>