changed ubuntu to an older version, for compatibility reasons with glibc on pyinstaller steps and added a step to parse the release tag

.github/workflows/release.yml

@@ -9,7 +9,7 @@ name: Upload Release Asset
 jobs:
   build:
     name: Upload Release Asset
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-16.04
     steps:
       - name: Checkout code
         uses: actions/checkout@v2
@@ -39,7 +39,17 @@ jobs:
           release_name: Release ${{ github.ref }}
           draft: false
           prerelease: false
-          
+      
+      # Beacause we can't easily parse the github.ref using github actions syntax, we extract it with an extra step
+      # Example:
+      # before - refs.tags.v0.3.1
+      # after - v0.3.1
+      - name: Parse Release Tag
+      - id: parse_release
+        run: |
+          release_tag=$(echo "refs.tags.v0.3.1" | sed -e "s/^refs.tags.//")
+          echo "::set-output name=release_tag::$release_tag"
+
       - name: Upload Release Asset
         id: upload-release-asset 
         uses: actions/upload-release-asset@v1
@@ -48,5 +58,5 @@ jobs:
         with:
           upload_url: ${{ steps.create_release.outputs.upload_url }}
           asset_path: ./dist/kube-hunter
-          asset_name: kube-hunter-linux-x86_64-${{ github.ref }}
+          asset_name: kube-hunter-linux-x86_64-${{ steps.parse_release.outputs.release_tag }}
           asset_content_type: application/octet-stream