migration: fix spice migration

migration: fix spice migration

Commit 29ae8a4133082e16970c9d4be09f4b6a15034617 ("rdma: introduce
MIG_STATE_NONE and change MIG_STATE_SETUP state transition") changed the
state transitions during migration setup.

Spice used to be notified with MIG_STATE_ACTIVE and it detected this
using migration_is_active().  Spice is now notified with
MIG_STATE_SETUP and migration_is_active() no longer works.

Replace migration_is_active() with migration_in_setup() to fix spice
migration.

Cc: Michael R. Hines <mrhines@us.ibm.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>