Option to disable auto discovery at the client VM level

Add an option to disable auto discovery at the client VM level via system property, i.e. -Dglobal.jnp.DisableDiscovery
This would complement existing jnp.DisableDiscovery property that can be passed to InitialContext() on creation.

The system property can be overriden by per InitialContext() jnp.DisableDiscovery property. Example:

• If no system propery is defined or is set to false:
• If jnp.DisableDiscovery not present or is defined as false, auto discovery will be attempted.
• If jnp.DisableDiscovery is present and is set to true, auto discovery will NOT be attempted (override default value).
• If system property is defined as true:
• If jnp.DisableDiscovery not present, auto discovery will NOT be attempted.
• If jnp.DisableDiscovery is present and is set to true, auto discovery will NOT be attempted.
• If jnp.DisableDiscovery is present and is set to false, auto discovery will be attempted (override default value).