HDDS-4891. Avoid latest/master in Github Actions (#1983)

diff --git a/.github/workflows/close-pending.yaml b/.github/workflows/close-pending.yaml
index 55444f7..87c633e 100644
--- a/.github/workflows/close-pending.yaml
+++ b/.github/workflows/close-pending.yaml
@@ -21,10 +21,10 @@
 jobs:
   close-pending:
     name: close-pending
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Checkout code
-        uses: actions/checkout@master
+        uses: actions/checkout@v2
       - name: Execute close-pending script
         if: github.repository == 'apache/ozone'
         run: ./.github/close-pending.sh
diff --git a/.github/workflows/comments.yaml b/.github/workflows/comments.yaml
index 2341662..62ae6ad 100644
--- a/.github/workflows/comments.yaml
+++ b/.github/workflows/comments.yaml
@@ -23,9 +23,11 @@
 jobs:
   process-comment:
     name: check-comment
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v2
-      - run: ./.github/process-comment.sh
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Execute process-comment script
+        run: ./.github/process-comment.sh
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}