Install python2 for Ubuntu 16.04 and CentOS 7 in Vagrant

Install python2 for Ubuntu 16.04 and CentOS 7 before executing test
script.

Change-Id: Ia57abe78ea0a525877a9ef607d91acd4fccdd02d

Vagrantfile

@@ -9,8 +9,6 @@ Vagrant.configure(2) do |config|
     xenial.vm.provision "shell", inline: <<-SHELL
       sudo su -
       cd /vagrant
-      apt-get update -y -qq
-      apt-get install -y python-pip
       ./run_tests.sh
     SHELL
   end

run_tests.sh

@@ -17,6 +17,15 @@ set -xeuo pipefail
 
 FUNCTIONAL_TEST=${FUNCTIONAL_TEST:-true}
 
+# Install python2 for Ubuntu 16.04 and CentOS 7
+if which apt-get; then
+    sudo apt-get update && sudo apt-get install -y python
+fi
+
+if which yum; then
+    sudo yum install -y python
+fi
+
 # Install pip.
 if ! which pip; then
   curl --silent --show-error --retry 5 \