Fix auto sheriff & append info messages for skipped targets (#1207)

diff --git a/buildkite/bazel_auto_sheriff.py b/buildkite/bazel_auto_sheriff.py
index 71cba12..63f15fd 100644
--- a/buildkite/bazel_auto_sheriff.py
+++ b/buildkite/bazel_auto_sheriff.py
@@ -628,7 +628,7 @@
 
     analyzers = []
     for project_name, project_info in bazelci.DOWNSTREAM_PROJECTS.items():
-        if "disabled_reason" not in project_info:
+        if project_name in downstream_result:
             analyzer = BuildInfoAnalyzer(project_name, project_info["pipeline_slug"], downstream_result[project_name])
             analyzers.append(analyzer)
             analyzer.start()
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 42572ea..2d594c6 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -2342,7 +2342,7 @@
         lines = ["The following tasks were skipped since they require specific Bazel versions:", ""]
         lines += ["- {}".format(s) for s in skipped_due_to_bazel_version]
         commands = [
-            "buildkite-agent annotate --style=info '{}' --context 'ctx-skipped_due_to_bazel_version'".format(
+            "buildkite-agent annotate --style=info '{}' --append --context 'ctx-skipped_due_to_bazel_version'".format(
                 "\n".join(lines)
             )
         ]