Don't overwrite kwargs in activities json

[will-moore]

Reported at ome/omero-figure#545

This fixes a bug introduced in #474, the kwargs parameter overwrites the kwargs from the function def activities(request, conn=None, **kwargs): causing various issues.

E.g. the detection of json template fails at

omero-web/omeroweb/webclient/views.py

Line 3930 in 4d8d25e

if "template" in kwargs and kwargs["template"] == "json":

so the format of the JSON returned to OMERO.figure is broken, as reported above.

To test:

• Open the developer Console in your browser
• Export a figure from OMERO.figure
• Check that the export completes and the Download button is shown with no errors in the Console

[knabar]

Verified that this fixes the issue with PathViewer