Drop redundant CpuBoundWork usage in JsonRpcConnection::Disconnect()

Although there is locking involved here, it shoudln't take too long for
the thread to actually acquire it, since there aren't that many threads
dealing with endpoint clients concurrently. It's just wasting pointless
time trying to obtain a CPU slot.

lib/remote/jsonrpcconnection.cpp

@@ -199,14 +199,14 @@ void JsonRpcConnection::Disconnect()
 			Log(LogWarning, "JsonRpcConnection")
 				<< "API client disconnected for identity '" << m_Identity << "'";
 
-			{
-				CpuBoundWork removeClient (yc);
-
-				if (m_Endpoint) {
-					m_Endpoint->RemoveClient(this);
-				} else {
-					ApiListener::GetInstance()->RemoveAnonymousClient(this);
-				}
+			// We need to unregister the endpoint client as soon as possible not to confuse Icinga 2,
+			// given that Endpoint::GetConnected() is just performing a check that the endpoint's client
+			// cache is not empty, which could result in an already disconnected endpoint never trying to
+			// reconnect again. See #7444.
+			if (m_Endpoint) {
+				m_Endpoint->RemoveClient(this);
+			} else {
+				ApiListener::GetInstance()->RemoveAnonymousClient(this);
 			}
 
 			m_OutgoingMessagesQueued.Set();