added default value for inSR=4326 to fix queries to arcgis server

when querying a map service layer and sending in the envelope geometry:

    {"xmin":90,"ymin":0,"xmax":112.5,"ymax":21.94304553343818,"spatialReference":{"wkid":4326}}

The inSR parameter also needed to be set to 4326 to successfully return features.  My guess is that this is a quirk in the arcgis server vs. arcgis online and that agol will successfully read the spatialReference from the envelope json itself, but that ArcGIS Server won't.