SSH: Take more care when closing channels.

We can't just pretend a channel is already gone after we request it to
close; it's only closed when the server has sent the acknowledgement.

Change-Id: Ib6e8b9bf77635995259885af13755f5fc0e825a9
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/libs/ssh/sshconnectionmanager.cpp

@@ -97,6 +97,8 @@ public:
                 continue;
 
             if (connection->thread() != QThread::currentThread()) {
+                if (connection->channelCount() != 0)
+                    continue;
                 QMetaObject::invokeMethod(this, "switchToCallerThread",
                     Qt::BlockingQueuedConnection,
                     Q_ARG(SshConnection *, connection),