Disable create tables before the shards of the cluster are fully allocated

[ZuLiangWang]

Description
In the current implementation, shards will start to be allocated when the number of nodes reaches the threshold, but only some shards are available for a period of time from the beginning to the completion of shards allocation. If there is a table creation request at this time, tables will be created on the allocated shards, it may result in uneven distribution of tables.

Proposal
Only after all the shards in the cluster are allocated can the table creation request be processed.

Additional context