Docker: Set future after connecting

Fixes a "QFutureWatcher::connect: connecting after calling setFuture()
is likely to produce race".

Amends 2a7bf0fdaf.

Change-Id: I69391984e2e583491bb978e41812b4f5a4c7b1a6
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

src/plugins/docker/dockerdevice.cpp

@@ -602,7 +602,6 @@ DockerDevice::DockerDevice()
         auto future = DockerApi::instance()->networks();
 
         auto watcher = new QFutureWatcher<expected_str<QList<Network>>>(this);
-        watcher->setFuture(future);
         QObject::connect(watcher,
                          &QFutureWatcher<expected_str<QList<Network>>>::finished,
                          this,
@@ -622,6 +621,7 @@ DockerDevice::DockerDevice()
                                  cb({errorItem});
                              }
                          });
+        watcher->setFuture(future);
     });
 
     connect(DockerApi::instance(),