parameterized build fix

To get a parameterized build to work we need to not pass in data and
expect that params == dictionary of of the parameters that should be
passed to requests.post method
IE
json_data = json.dumps({'parameter':[{'name':'MyVarString',
'value':'Hello World'}]})
params = {'data':{'json':json_data},'headers':{'Content-Type':
'application/x-www-form-urlencoded'}}
jenk.build_job('TestBuild',params=params)