Ambiguity of config `session_idle_timeout_secs`

[jie.wang]

It seems that config session_idle_timeout_secs set the max idle time of the session. But actually, it records the time since a session is created, even if the session is not idle(eg. executing queries).

Reproduce:
set session_idle_timeout_secs to 10s, and then execute a slow query. After session_idle_timeout_secs and at next session_reclaim_interval_secs, the query will be killed

[cpw]

session_reclaim_interval_secs, nebula will try to reclaim sessions every session_reclaim_interval_secs.
session_idle_timeout_secs , nebula will count the idle time of session, if the real idle time greater than session_idle_timeout_secs, nebula will expires it at the next period of session_reclaim_interval_secs.

We will not kill the query actively, unless users demands it explicitely.