idle_session_pool_time=0s doesn't immediately pool idle connections

When configured with idle_session_pool_time=0s, the connections will only be put into the
pool once they have been idle longer than the configured time. Since the comparison is done at one second granularity, a connection would have to be idle for more than a second for it to be put into the pool.

The interpretation of the value should be changed to use greater-than-or-equal semantics instead of the current greater-than semantics. Additionally, the granularity can be changed to use the internal ticks of 100 milliseconds.