[Findit] don't included skipped or unknown tests in swarming tasks into failed tests.

appengine/findit/waterfall/test/data/m_b_223_abc_test.json

 {
     "disabled_tests": [],
     "global_tags": [],
     "all_tests": [
         "Unittest1.Subtest1",
         "Unittest1.Subtest2",
         "Unittest2.Subtest1",
         "Unittest2.Subtest2",
         "Unittest3.Subtest1",
         "Unittest3.Subtest2",
@@ skipping 61 matching lines @@
                     "output_snippet": "ERROR:x_test.cc:1234\\na/b/u2s1.cc:567: Failure\\n",
                     "status": "FAILURE",
                     "output_snippet_base64": "RVJST1I6eF90ZXN0LmNjOjEyMzQKYS9iL3UyczEuY2M6NTY3OiBGYWlsdXJlCg=="
                 }
             ],
             "Unittest2.Subtest2": [
                 {
                     "elapsed_time_ms": 1,
                     "losless_snippet": true,
                     "output_snippet": "[       OK ]\\n",
-                    "status": "SUCCESS",
+                    "status": "SKIPPED",
                     "output_snippet_base64": "WyAgICAgICBPSyBdCg=="
                 }
             ],
             "Unittest3.Subtest1": [
                 {
                     "elapsed_time_ms": 1,
                     "losless_snippet": true,
                     "output_snippet": "[       OK ]\\n",
                     "status": "SUCCESS",
                     "output_snippet_base64": "WyAgICAgICBPSyBdCg=="
@@ skipping 34 matching lines @@
                     "elapsed_time_ms": 1,
                     "losless_snippet": true,
                     "output_snippet": "[       OK ]\\n",
                     "status": "SUCCESS",
                     "output_snippet_base64": "WyAgICAgICBPSyBdCg=="
                 }
             ]
         }
     ]
 }