Make create schema effective in real time

[sun361504834]

now trying to insert data with a newly created tag may fail,
because the creation of the tag/property is implemented asynchronously. (Wait for two heartbeat cycles, i.e., 20 seconds.)

we need support create schema effective in real time, Can it be implemented synchronously?

Thanks!
@MuYiYong

[wey-gu]

Now the schema change is "pull-ed" via the periodic heartbeat communication.

We could think of adding "best-effort push with timestamp" to update schema in all storageD, that is, it's still async update, and in the worst case the push didn't succeed, still it will be updated by heartbeat later in two cycles, while when it's pushed successfully, the user will have experience of real-time schema altering :).