A_SYB_NO_DBCLOSE configuration variable

When the run time is shutting down, the interface closes all the open connections, as per the Microsoft documentation. Sometimes, with some network drivers, this takes a significant amount of time. Setting this variable ON causes the interface not to close the connections. Though this can speed up the runtime (during shutdown), we don’t recommended it, because the Microsoft documentation is not being followed. While the default value is OFF (FALSE, NO), this configuration variable can also take the value of ON (TRUE, YES).