Conditions for automatic server shutdown

Certain conditions will cause the PingDirectory servers to shut down.

All PingDirectory servers will shut down if any of the following occur:

Server runs out of memory condition
Low disk space error state
Server runs out of file descriptors

Configuring the PingDirectory server to shut down instead of lock down

The PingDirectory server will enter lockdown mode on unrecoverable database environment errors, but can be configured to shutdown instead with this setting:
```
$ dsconfig set-global-configuration-prop \
  --set unrecoverable-database-error-mode:initiate-server-shutdown
```