`reload @@config_all` twice error

[actiontech-bot]

Raised by: @zhunina
The second reload @@config_all will return error: ERROR 1003 (HY000):The before reload @@config_all has an unfinished db transaction,please try again later

[actiontech-bot]

By @yanhuqing666

Before:
reload @@config_all will recycle all connections async.
It will try to recycle only the timeout (sqlExecuteTimeout, default is 300s ) connections every 5s.
Before all connections are recycled, the second reload @@config_all will throw error.

Fixed:
reload @@config_all will recycle processing connections async.
It will try to recycle connections which is timeout or whose processing transaction is done every 5s.
Before all connections are recycled, the second reload @@config_all will throw error.

[actiontech-bot]

By @yanhuqing666

Atomic is not guaranteed yet.

[zhunina]

fixed