Fix connection_life_time does not work.

Fix connection_life_time does not work.

If master node is not 0 (this could happen in the case when primary
node is not 0 in streaming replication mode for example), pgpool
failed to find connection_life_time timer because the timer was set
only in virtual_master_node, which could be changed after session ends
since query context is not there any more.

To fix this, connection_life_time timer is set to all valid nodes.

Regression test is also added.

Discussion: https://www.pgpool.net/pipermail/pgpool-general/2020-August/007242.html