rgw: Initialize pointer field in seed
Fixes the Coverity Scan Report:
CID
1396116: Uninitialized pointer field (UNINIT_CTOR)
2. uninit_member: Non-static class member create_date is not initialized in this constructor nor in any functions that it calls.
4. uninit_member: Non-static class member s is not initialized in this constructor nor in any functions that it calls.
6. uninit_member: Non-static class member store is not initialized in this constructor nor in any functions that it calls.
Signed-off-by: Jos Collin <jcollin@redhat.com>