qemu: checkpoint: fix NULL dereference at create time

'cfg' is never initialized here, which causes a crash
later in qemuCheckpointCreateFinalize
Reviewed-by: NPeter Krempa <pkrempa@redhat.com>
Signed-off-by: NCole Robinson <crobinso@redhat.com>

src/qemu/qemu_checkpoint.c

@@ -464,7 +464,7 @@ qemuCheckpointCreateXML(virDomainPtr domain,
     bool update_current = true;
     bool redefine = flags & VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE;
     unsigned int parse_flags = 0;
-    g_autoptr(virQEMUDriverConfig) cfg = NULL;
+    g_autoptr(virQEMUDriverConfig) cfg = virQEMUDriverGetConfig(driver);
     g_autoptr(virDomainCheckpointDef) def = NULL;
 
     virCheckFlags(VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE, NULL);