Permission about table snapshot operations

[liushaohui]

hi all:

In current codebase, the table snapshot operations only can be done by 
the global admin ,
not by  the table admin. Please see:AccessController.java# 1175.
Is there any special purposes to limit the table admin to do snapshot 
operations?

Here is our scenario:

There is a big share hbase cluster.
Each table has different snapshot policies, eg: do snapshot per week, or 
snapshot after the new data are imported.
We want to release the snapshot permission to each table admin.

Suggestions and discussions are welcomed.

Thanks

-Shaohui Liu from xiaomi.com