Install python3 instead of python2 during host bootstrapping.

Also use ansible interpreter discovery rather than hardcoding the
path to the python executable which may vary depending on distro.

Change-Id: Id6d1ec65106b5b8eabb152b0238a6f9c0a2d97da

tests/bootstrap-aio.yml

@@ -24,7 +24,6 @@
     - "{{ playbook_dir }}/../playbooks/defaults/repo_packages/openstack_services.yml"
   environment: "{{ deployment_environment_variables | default({}) }}"
   vars:
-    ansible_python_interpreter: "/usr/bin/python"
     sftp_subsystem:
         'apt': 'sftp /usr/lib/openssh/sftp-server'
         'yum': 'sftp /usr/libexec/openssh/sftp-server'

tests/roles/bootstrap-host/vars/debian.yml

@@ -25,11 +25,11 @@ packages_install:
   - git-core
   - iptables
   - iputils-tracepath
-  - ipython
+  - ipython3
   - lvm2
   - parted
-  - python2.7
-  - python-dev
+  - python3
+  - python3-dev
   - sshpass
   - vim
   - vlan

tests/roles/bootstrap-host/vars/redhat.yml

@@ -22,8 +22,8 @@ packages_install:
   - git
   - iputils
   - lvm2
-  - python
-  - python-devel
+  - python3
+  - python3-devel
   - sshpass
   - systemd-networkd
   - vim

tests/roles/bootstrap-host/vars/suse.yml

@@ -23,8 +23,8 @@ packages_install:
   - git-core
   - iptables
   - lvm2
-  - python
-  - python-devel
+  - python3
+  - python3-devel
   - vim
   - vlan
   - xfsprogs