ecbd4bcae0
1. If the table or db has been dropped，we will get write lock failed or just skip or throw exception，
2. and if we recover table or db， we must ensure that unmark dropped state after writing recover journal.
3. db.dropTable corresponds to db.createTable, I don't move table.markDropped method to the db.dropTable,
for that all meta added to db or catalog must after writing recover journal, so we must invoke markDropped
and unmarkDropped method outside the dropTable and createTable method.