qemu: remove nonsensical sanity check in processNetdevStreamDisconnectedEvent()

qemu: remove nonsensical sanity check in processNetdevStreamDisconnectedEvent()

By definition QEMU will never send a NETDEV_STREAM_DISCONNECTED event
if it doesn't support the reconnect option for a stream netdev. And
even if, by some comedy of errors, it did send
NETDEV_STREAM_DISCONNECTED in that case, our response to the event
doesn't request anything at all of QEMU (much less something that
would fail if QEMU didn't understand NETDEV_STREAM_DISCONNECTED) - it
just starts a new passt process to replace the one that has been
terminated, so we don't need to check the QEMU capabilities for
QEMU_CAPS_NETDEV_STREAM_RECONNECT.

Signed-off-by: Laine Stump <laine@redhat.com>
Tested-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>