migration: Move channel setup out of postcopy_try_recover()

migration: Move channel setup out of postcopy_try_recover()

We used to use postcopy_try_recover() to replace migration_incoming_setup() to
setup incoming channels.  That's fine for the old world, but in the new world
there can be more than one channels that need setup.  Better move the channel
setup out of it so that postcopy_try_recover() only handles the last phase of
switching to the recovery phase.

To do that in migration_fd_process_incoming(), move the postcopy_try_recover()
call to be after migration_incoming_setup(), which will setup the channels.
While in migration_ioc_process_incoming(), postpone the recover() routine right
before we'll jump into migration_incoming_process().

A side benefit is we don't need to pass in QEMUFile* to postcopy_try_recover()
anymore.  Remove it.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220331150857.74406-7-peterx@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>