Description of problem:
In xmlrpc doc, key "category" is not available for TestCaseRun.filter(). 
Actually, it doesn't work.

TestCaseRun.filter() can not filter caserun via "category".

Version-Release number of selected component (if applicable):
3.8 on stage/production

How reproducible:


Steps to Reproduce:
1. TestCaseRun.filter({'category__name': "xgaoxgaoxgao"})
 or TestCaseRun.filter({'category__id': 261})

2.
3.
  
Actual results:
Fault: <Fault 1: "FieldError: Cannot resolve keyword 'category' into field. Choices are: assignee, build, case, case_run_attachment, case_run_bug, case_run_id, case_run_status, case_text_version, close_date, environment_id, is_current, links, notes, run, running_date, sortkey, tested_by">


Expected results:
After reviewed code, I couldn't found the attribute "category" in the class "TestCaseRun". So I suggest remove  key "category" from doc. And if user want to filter case via category, they can use key "case", for example, 
>>> TestCaseRun.filter({'case__category__name': "xgaoxgaoxgao"})
or
>>> TestCaseRun.filter({'case__category__id': 261})

Additional info: