driver: SigrokDriver capture file is transferred to wrong path

when specified filename is not absolute and using a remote sigrok resource

Usually when an absolute path is supplied as `filename`
the call `abs.path.join()` resolves to `filename`.
But when the file path is relative,
it resolves it to a relative path appended to the tmp dir,
instead of from where the user calls this method.

Signed-off-by: Felix Zwettler <felix.zwettler@duagon.com>

Author: flxzt

labgrid/driver/sigrokdriver.py

@@ -179,7 +179,7 @@ def stop(self):
         if isinstance(self.sigrok, NetworkSigrokUSBDevice):
             subprocess.call([
                 'scp', f'{self.sigrok.host}:{os.path.join(self._tmpdir, self._basename)}',
-                os.path.join(self._local_tmpdir, self._filename)
+                os.path.abspath(self._filename)
             ],
                             stdin=subprocess.DEVNULL,
                             stdout=subprocess.DEVNULL,