cls/rbd: use brace initialization in cls_rbd_snap::generate_test_instances()

in ed6b712, we switched some of them to explicit call of constructor to
study some compiling failures, but forgot to revert to the original
version after the failures were addressed.

in this change, we revert them to the original version to be more consistent.

Signed-off-by: Kefu Chai <[email protected]>

Author: tchaikov

src/cls/rbd/cls_rbd.h

@@ -234,11 +234,11 @@ struct cls_rbd_snap {
     // otherwise check-generated.sh would fail due to the disprepancies between
     // the original dump and re-encoded dump
     o.push_back(cls_rbd_snap{1, "snap", 123456,
-                             RBD_PROTECTION_STATUS_PROTECTED, cls_rbd_parent{}, 31, {},
+                             RBD_PROTECTION_STATUS_PROTECTED, {}, 31, {},
                              cls::rbd::UserSnapshotNamespace{}, 543, {}});
     o.push_back(cls_rbd_snap{1, "snap", 123456,
-                             RBD_PROTECTION_STATUS_PROTECTED, cls_rbd_parent{}, 31, utime_t{},
-                             cls::rbd::UserSnapshotNamespace{}, 543, std::optional<uint64_t>{0}});
+                             RBD_PROTECTION_STATUS_PROTECTED, {}, 31, {},
+                             cls::rbd::UserSnapshotNamespace{}, 543, {0}});
     o.push_back(cls_rbd_snap{1, "snap", 123456,
                              RBD_PROTECTION_STATUS_PROTECTED, {}, 31, {},
                              cls::rbd::UserSnapshotNamespace{}, 543, {123}});