migration: Don't leak IO channels
    
    Since qemu_fopen_channel_{in,out}put take references on the underlying
    IO channels, make sure to release our references to them.
    
    Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
    Message-Id: <20171101142526.1006-2-ross.lagerwall@citrix.com>
    Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
    Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
    (cherry picked from commit 032b79f7173051e7f8742a43d106c7fc526856f9)
    Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>