block/parallels: Do not update header or truncate image when INMIGRATE

block/parallels: Do not update header or truncate image when INMIGRATE

If we write or modify the image file while the QEMU run state is
INMIGRATE, then the BDRV_O_INACTIVE BDS flag is set.  This will cause
an assert, since the image is marked inactive.  Make sure we obey this
flag.

Tested-by: Alexey Kardashevskiy <[email protected]>
Signed-off-by: Jeff Cody <[email protected]>
Message-id: 3996c930fa8cde8570b7a63032720d76a28fd78b.1510059970[email protected]
Reviewed-by: Stefan Hajnoczi <[email protected]>
Reviewed-by: Denis V. Lunev <[email protected]>
Signed-off-by: Max Reitz <[email protected]>