ssa_path_record_data.c: Use ssa_db_get_epoch function in ssa_pr_rebuild_indexes

Until partial update is implemented, epoch is database
attribute rather than table's attribute.

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>