RemoteLinux: Use an SshProcess for rsync

Otherwise, if connection sharing is disabled and public key
authentication fails, the askpass tool is not invoked.

Change-Id: Iea8316675b8f270c924f822f340f6282b21450d5
Reviewed-by: hjk <hjk@qt.io>

src/plugins/remotelinux/linuxdevicetester.cpp

@@ -55,7 +55,7 @@ public:
     SshRemoteProcessPtr process;
     DeviceUsedPortsGatherer portsGatherer;
     SftpSessionPtr sftpSession;
-    QProcess rsyncProcess;
+    SshProcess rsyncProcess;
     State state = Inactive;
     bool sftpWorks = false;
 };