Bug 849750

Right now there is no "clean" way to remove an agent in certain circumstances. If an agent is configured, but nothing is imported, then the discovery queue is not cleared out if the agent is subsequently deleted. Also, if an agent is created and then removed, it is difficult to re-create the agent properly; there can be conflicts because of a missing security token or naming conflicts.

This is tangential to bug 828904, but that bug shows the related question of a ghost discovery queue.

So, there needs to be a better procedure described for (1) removing an agent from the topology and (2) restoring an agent.

Affected doc:
* Install guide: https://access.redhat.com/knowledge/docs/en-US/JBoss_Operations_Network/3.1/html/Installation_Guide/uninstall.html#uninstall-agent
* FAQ: https://access.redhat.com/knowledge/docs/en-US/JBoss_Operations_Network/3.1/html/Frequently_Asked_Questions/index.html#qa29 (and possibly others) 
* Server/agent guide: https://access.redhat.com/knowledge/docs/en-US/JBoss_Operations_Network/3.1/html/Admin_Configuring_JON_Servers_and_Agents/agent-config.html#registering-agent

Details for the docs:
There are two paths that can be taken, and they are mutually exclusive.

P A T H   # 1
--------------
Scenario:
* the agent persisted config should be purged
* the agent's inventory should be purged
* the agent / platform has been removed from the JON inventory

Option:
Use --fullcleanconfig to force the agent to reconfigure itself and re-register with the server.

Potential error:
* If the agent is still in the inventory, this fails with an invalid security token.


P A T H   # 2
--------------
Scenario:
* the agent persisted config should be purged
* the agent's inventory should NOT be purged
* the agent / platform REMAINS IN the JON inventory
* the agent name remains the same

Option:
Use --cleanconfig to force the agent to reconfigure itself and re-register with the server.

Potential error:
* If the agent name changes (like, a re-install that doesn't use the default), it fails because the security token is validated against the agent's name.



R E C O M M E N D E D   C H A N G E S
--------------------------------------
1. Update the "uninstall an agent" section so that the agent can be uninstalled cleanly.

2. Update all FAQs that deal with reconfiguring an agent.

3. Expand both the agent install section (install guide) and agent re-registration section (server/agent guide) to better describe the two different re-registration paths.