ci: specify ubuntu version to make github action happy

actions/runner-images#1816

(cherry picked from commit e3082cd)

.github/workflows/build-arm64-image.yaml

@@ -17,7 +17,7 @@ on:
 jobs:
   build:
     name: Build arm64
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Set up Go 1.x
         uses: actions/setup-go@v2

.github/workflows/build-dpdk-image.yaml

@@ -17,7 +17,7 @@ on:
 jobs:
   build:
     name: Build DPDK
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Check out code
         uses: actions/checkout@v2

.github/workflows/build-x86-image.yaml

@@ -18,7 +18,7 @@ on:
 jobs:
   build:
     name: Build x86
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Set up Go 1.x
         uses: actions/setup-go@v2
@@ -78,7 +78,7 @@ jobs:
   single-e2e:
     needs: build
     name: 1-master-e2e
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Check out code
         uses: actions/checkout@v2
@@ -124,7 +124,7 @@ jobs:
   ha-e2e:
     needs: build
     name: 3-master-e2e
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Check out code
         uses: actions/checkout@v2
@@ -171,7 +171,7 @@ jobs:
   ipv6-e2e:
     needs: build
     name: ipv6-e2e
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Check out code
         uses: actions/checkout@v2
@@ -207,7 +207,7 @@ jobs:
   push:
     needs: [single-e2e, ha-e2e, ipv6-e2e]
     name: push
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
       - name: Check out code
         uses: actions/checkout@v2

.github/workflows/codeql-analysis.yml

@@ -0,0 +1,71 @@
+# For most projects, this workflow file will not need changing; you simply need
+# to commit it to your repository.
+#
+# You may wish to alter this file to override the set of languages analyzed,
+# or to provide custom queries or build logic.
+name: "CodeQL"
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [master]
+  schedule:
+    - cron: '0 17 * * 2'
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-18.04
+
+    strategy:
+      fail-fast: false
+      matrix:
+        # Override automatic language detection by changing the below list
+        # Supported options are ['csharp', 'cpp', 'go', 'java', 'javascript', 'python']
+        language: ['go']
+        # Learn more...
+        # https://docs.github.com/en/github/finding-security-vulnerabilities-and-errors-in-your-code/configuring-code-scanning#overriding-automatic-language-detection
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+      with:
+        # We must fetch at least the immediate parents so that if this is
+        # a pull request then we can checkout the head.
+        fetch-depth: 2
+
+    # If this run was triggered by a pull request event, then checkout
+    # the head of the pull request instead of the merge commit.
+    - run: git checkout HEAD^2
+      if: ${{ github.event_name == 'pull_request' }}
+
+    # Initializes the CodeQL tools for scanning.
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: ${{ matrix.language }}
+        # If you wish to specify custom queries, you can do so here or in a config file.
+        # By default, queries listed here will override any specified in a config file. 
+        # Prefix the list here with "+" to use these queries and those in the config file.
+        # queries: ./path/to/local/query, your-org/your-repo/queries@main
+
+    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
+    # If this step fails, then you should remove it and run the build manually (see below)
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v1
+
+    # ℹ️ Command-line programs to run using the OS shell.
+    # 📚 https://git.io/JvXDl
+
+    # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
+    #    and modify them (or add more) to build your code if your project
+    #    uses a compiled language
+
+    #- run: |
+    #   make bootstrap
+    #   make release
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1