qemu: fix broken handling of shallow flag in qemuDomainBlockCopyCommon

Commit 16ca234b refactored how the 'shallow' and 'reuse' flags
are accessed but neglected to fix the clearing of 'shallow' in case when
the disk has no backing chain. This means that we'd request a shallow
copy even without backing chain and also a few checks would work wrong.

Fix it by using the extracted variable everywhere.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_driver.c

@@ -18299,12 +18299,9 @@ qemuDomainBlockCopyValidateMirror(virStorageSourcePtr mirror,
  */
 static int
 qemuDomainBlockCopyCommonValidateUserMirrorBackingStore(virStorageSourcePtr mirror,
-                                                        unsigned int flags,
+                                                        bool shallow,
                                                         bool blockdev)
 {
-    /* note that if original disk does not have backing chain, shallow is cleared */
-    bool shallow = flags & VIR_DOMAIN_BLOCK_COPY_SHALLOW;
-
     if (!virStorageSourceHasBacking(mirror)) {
         /* for deep copy there won't be backing chain so we can terminate it */
         if (!mirror->backingStore &&
@@ -18417,9 +18414,10 @@ qemuDomainBlockCopyCommon(virDomainObjPtr vm,
 
     /* clear the _SHALLOW flag if there is only one layer */
     if (!virStorageSourceHasBacking(disk->src))
-        flags &= ~VIR_DOMAIN_BLOCK_COPY_SHALLOW;
+        mirror_shallow = false;
 
-    if (qemuDomainBlockCopyCommonValidateUserMirrorBackingStore(mirror, flags,
+    if (qemuDomainBlockCopyCommonValidateUserMirrorBackingStore(mirror,
+                                                                mirror_shallow,
                                                                 blockdev) < 0)
         goto endjob;