qemu: domain: Convert detected 'iso' image format into 'raw'

While our code can detect ISO as a separate format, qemu does not use it
as such and just passes it through as raw. Add conversion for detected
parts of the backing chain so that the validation code does not reject
it right away.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

src/qemu/qemu_domain.c

@@ -11493,6 +11493,10 @@ qemuDomainDetermineDiskChain(virQEMUDriverPtr driver,
         return -1;
 
     for (n = src->backingStore; virStorageSourceIsBacking(n); n = n->backingStore) {
+        /* convert detected ISO format to 'raw' as qemu would not understand it */
+        if (n->format == VIR_STORAGE_FILE_ISO)
+            n->format = VIR_STORAGE_FILE_RAW;
+
         if (qemuDomainValidateStorageSource(n, priv->qemuCaps) < 0)
             return -1;