migration: Create migration_ioc_process_incoming()

migration: Create migration_ioc_process_incoming()

We pass the ioc instead of the fd.  This will allow us to have more
than one channel open.  We also make sure that we set the
from_src_file sooner, so we don't need to pass it as a parameter.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
--

Do not assing mis->from_src_file (peterxu)