Ensure client includes AgentDescription on Reconnect

[dsvanlani]

Resolves: #55

This PR ensures that the client includes AgentDescription every time it connects to the server, not just after client.Start.

Current behavior:

• Clients connection to server is interrupted.
• Client reconnects.
• Client does not prepare a "first status message" with an AgentDescription.

Expected behavior:

• Clients connection to server is interrupted.
• Client reconnects.
• Client prepares and sends a status including AgentDescription.

[andykellr]

I collaborated with @dsvanlani on this fix so I would appreciate another review.

[tigrannajaryan]

LGTM

[tigrannajaryan]

Thanks for the fix.

[tigrannajaryan]

I may have been too quick to merge this.

Re-reading the spec, it says:

The Agent MUST send a status report:
* First time immediately after connecting to the Server. The status report MUST
  be the first message sent by the Agent.
* Subsequently every time the status of the Agent changes.

Nowhere does it says that the AgentDescription must be also included in the status report. On the contrary, the spec says:

<h4 id="agent_description">agent_description</h4>

The description of the agent, its type, where it runs, etc. See
[AgentDescription](#agentdescription-message) message for details.

This field SHOULD be unset if no Agent description fields have changed since the
last StatusReport was sent.

So, this fix it correct that it sends the status report after reconnect (it was a bug that we didn't), but we now unnecessarily include the AgentDescription in these subsequent status reports.

@dsvanlani Can you do a follow-up PR that corrects this behavior?