RemoteLinux: Use a structure to return check results

Instead of the combined bool value + QString * out parameter.

Change-Id: I8840f48b74aaacd1b0c0412efd8abcdc2be12d58
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/remotelinux/rsyncdeploystep.h

@@ -57,7 +57,7 @@ private:
     AbstractRemoteLinuxDeployService *deployService() const override;
     void doRun() override;
 
-    bool initInternal(QString *error = nullptr) override;
+    CheckResult initInternal() override;
 
     class RsyncDeployStepPrivate;
     RsyncDeployStepPrivate * const d;