BUG#23742339 FAILING ASSERTION: SYM_NODE->TABLE != NULL

Analysis: When we access fts aux tables in information schema,the
fts aux tables are dropped by DROP DATABASE in another session.

Solution: Drop parent table if it's a fts aux table, and drop
table will drop fts aux tables together.
Reviewed-by: Jimmy Yang <jimmy.yang@oracle.com>
RB: 13264