[current results] Do not store skipped tests in current results database

When a test is skipped on a configuration for the first time,
the change is reported as a changed result with new result "skipped".
Subsequent builder runs remove this skipped record completely.
Ignore these test results in the current results server.

Bug: #107
Change-Id: I8587aab909fd367edc642f4a97513ca1a39e0592
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/339921
Reviewed-by: Alexander Thomas <[email protected]>

Author: whesse

current_results/lib/src/slice.dart

@@ -74,6 +74,7 @@ class Slice {
       final result = Result.fromApi(api.Result()
         ..mergeFromProto3Json(json.decode(line),
             supportNamesWithUnderscores: true));
+      if (result.result == 'skipped') continue;
       if (configuration == null) {
         configuration = result.configuration;
       } else if (result.configuration != configuration) {