Fixing KeyError issue

The Jira ticket is:

https://arraynetworks.atlassian.net/browse/TWSD-1036
The error message is:

ERROR - Internal Server Error: /apv.fcgi/api/avx/network/vswitch/VirtualSwitchVA/_add
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/django/core/handlers/base.py", line 113, in get_response
    response = callback(request, *callback_args, **callback_kwargs)
  File "/ca/webui/htdocs/new/src/hive/router.py", line 253, in hive_ajax_router
    response = HttpResponse(ModelAjaxHandler(request, sess, app, model, action).render())
  File "/ca/webui/htdocs/new/src/hive/model/ajax.py", line 47, in render
    return getattr(self, self.action)(**request_dict)
  File "/ca/webui/htdocs/new/src/hive/model/ajax.py", line 176, in add
    self.manager.insert(new_obj)
  File "/ca/webui/htdocs/new/src/hive/model/manager.py", line 218, in insert
    result = self._insert(model_instance)
  File "/ca/webui/htdocs/new/src/avx/models/network/vswitch/__init__.py", line 301, in _insert
    data = instance.get_field_dict()
  File "/ca/webui/htdocs/new/src/hive/model/base.py", line 587, in get_field_dict
    val = mgr.get_field_by_instance(self, f.attname)
  File "/ca/webui/htdocs/new/src/hive/model/manager.py", line 592, in get_field_by_instance
    the_instance = data.get(the_pk_dict)
  File "/ca/webui/htdocs/new/src/hive/model/query.py", line 72, in get
    return self.__getitem__(pk_str)
  File "/ca/webui/htdocs/new/src/hive/model/query.py", line 126, in __getitem__
    return self._cache_dict[k]
KeyError: '{"va": [{"_asso_idx": 0, "va_name": "M_custom_apv"}], "vport": "vport1", "vs_name": [{"_asso_idx": 0, "name": "test"}]}'
The root cause is there is no key in the _cache_dict,

so I used instance itself instead of transfer to dictionary,

then it won't try to get cache data and cause KeyError.

Besides,

because the fields are AssoFields, that is,

not primitive type(string or integer, boolean...),

if the key is a list such as [{"_asso_idx": 0, "va_name": "M_custom_apv"}],

it may not find the key in Python2.7.

Thus,

use instance is better than transfering it to dictionary.