virStorageSourceChainHasManagedPR: Check propely

In the virStorageSourceChainHasManagedPR() function we iterate
over whole backing chain trying to determine if one of the layers
has managed PR configured. But due to a typo we in fact check the
top layer only.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/util/virstoragefile.c

@@ -2083,7 +2083,7 @@ virStorageSourceChainHasManagedPR(virStorageSourcePtr src)
     virStorageSourcePtr n;
 
     for (n = src; virStorageSourceIsBacking(n); n = n->backingStore) {
-        if (virStoragePRDefIsManaged(src->pr))
+        if (virStoragePRDefIsManaged(n->pr))
             return true;
     }