call dict.__init__() in OrderedDict.__init__()

Best-practice; squelches a pylint warning. Did this before in #4716, but that seems to have been lost during the switch to a different `OrderedDict` recipe.
```
************* Module salt.utils.odict
W0231: 50,12:OrderedDict.__init__: __init__ method from base class 'dict' is not called
```