resend terminal disconnect

Summary:
- if we are in the process of connecting when user invokes async_disconnect we should send a disconnect packet after connect completes
- move integration disconnect tests to integration folder

Reviewers: ivica

Reviewed By: ivica

Subscribers: korina

Differential Revision: https://repo.mireo.local/D28119

include/async_mqtt5/mqtt_client.hpp

@@ -872,8 +872,8 @@ public:
 	 *
 	 *	\par Completion condition
 	 *	The asynchronous operation will complete when one of the following conditions is true:\n
-	 *		- The Client has attempted to send a \__DISCONNECT\__ packet, regardless of whether
-	 *		the sending was successful or not.\n
+	 *		- The Client has sent a \__DISCONNECT\__ packet.\n
+	 *		- 5 seconds have elapsed without a successful send.\n
 	 *		- An error occurred. This is indicated by an associated \__ERROR_CODE\__ in the handler.\n
 	 *
 	 *	\par Error codes