qemu: Remove managed save flag from VM when starting with --force-boot

At the start of the guest after the image is unlinked the state wasn't
touched up to match the state on disk.

src/qemu/qemu_driver.c

@@ -5428,6 +5428,7 @@ qemuDomainObjStart(virConnectPtr conn,
                                      managed_save);
                 goto cleanup;
             }
+            vm->hasManagedSave = false;
         } else {
             ret = qemuDomainObjRestore(conn, driver, vm, managed_save,
                                        start_paused, bypass_cache);