GitHub Actions: add installation of dnf config-manager for CentOS 8

Author: Lukas955

.github/workflows/main.yml

@@ -33,6 +33,7 @@ jobs:
     - name: Enable additional repositories (CentOS 8)
       if: startsWith(matrix.image, 'centos:8')
       run: |
+        dnf install 'dnf-command(config-manager)'
         dnf config-manager --set-enabled AppStream PowerTools
     - name: Install dependencies  for libfds and IPFIXcol2 (CentOS)
       if: startsWith(matrix.image, 'centos')

.github/workflows/packages.yml

@@ -102,6 +102,7 @@ jobs:
     - name: Enable additional repositories (CentOS 8)
       if: startsWith(matrix.image, 'centos:8')
       run: |
+        dnf install 'dnf-command(config-manager)'
         dnf config-manager --set-enabled AppStream PowerTools
     - name: Install dependencies for libfds and IPFIXcol2 (CentOS)
       if: startsWith(matrix.image, 'centos')