By adding the instrument to the Alazarparameter, the ATSinstrument be…

…comes serializable. (#509)

The AlazarParameter were non serializable because an explicit reference was stored.
The way that baseparameter works, now only the name is stored

qcodes/instrument_drivers/AlazarTech/ATS.py

@@ -793,7 +793,8 @@ def __init__(self, name=None, label=None, unit=None, instrument=None,
                 # TODO(damazter) (S) test this validator
                 vals = validators.Enum(*byte_to_value_dict.values())
 
-        super().__init__(name=name, label=label, units=unit, vals=vals)
+        super().__init__(name=name, label=label, units=unit, vals=vals,
+                         instrument=instrument)
         self.instrument = instrument
         self._byte = None
         self._uptodate_flag = False