Bug in get_connection

[Izayda]

If in odbc_kwargs key 'servername' is passed, error "TypeError: get_connection() got multiple values for keyword argument 'servername'" occurs.

it occurs here:

   connection = pyodbc.connect(**kwargs)

    if reconnect:
        return get_connection(
            reconnect=False,
            servername=_get_random_node_address(connection),
            **kwargs
        )

Test example:

def a(bool_clause=True,**kwargs):
    x=kwargs
    if bool_clause:
       x=a(bool_clause=False,servername='good string',**kwargs)
    return x


print a(a=True,**{'servername':'bad string','Database':'testDB'})

There are different ways of fixing it, so i didn't create a pull request.

Thanks for a pyvertica, it's great!)