Add ubuntu 22.04 to CI workflow (#1169)

- run-tests: test ubuntu 22.04 with python 3.x
- install.sh: add cgroupfs-mount to dependencies

.github/workflows/run-tests.yaml

@@ -9,8 +9,13 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04]
+        include:
-        python-version: [3.x, 2.x]
+          - os: ubuntu-22.04
+            python-version: 3.x
+          - os: ubuntu-20.04
+            python-version: 3.x
+          - os: ubuntu-20.04
+            python-version: 2.x
     steps:
       - name: Check out Mininet source
         uses: actions/checkout@v2

util/install.sh

@@ -205,6 +205,7 @@ function mn_deps {
         fi
         $install iproute2 || $install iproute
         $install cgroup-tools || $install cgroup-bin
+        $install cgroupfs-mount
     fi
 
     echo "Installing Mininet core"