Added changes to support and enable installation of SODA on Ubuntu20.04

[anvithks]

What type of PR is this?
/kind new feature

What this PR does / why we need it:
This PR enables installation of SODA on Ubuntu 20.04.

• Python2 is deprecated in Ubuntu20.04 and not available. All python-pip installations are upgraded to python3-pip
• All scripts running python2 scripts are now executed with python3
• Ansible version is updated to 2.9.6 (The default supported version for the ceph-ansible version supported)
• Changed the ansible variable syntax to updated syntax for Ansible 2.9. Changed usage of single and double quotes.
• install_as_systemd is set to false. Bring api, controller and dock as standalone processes.
• Added an other variable called install_etcd_as_systemd and set it to false. etcd is also brought up as a standalone process.
• Updated the CI to work on the ubuntu2004-experimental branch.
• Removed the CI check for install from repository. Currently on install from release is tested with Ubuntu20.04

Which issue(s) this PR fixes:
Fixes #485

Test Report Added?:
/kind TESTED

Test Report:
Tested on Ubuntu 20.04 on Virtual Box.

Special notes for your reviewer:
There are some issues with the Anisble installation and etcd service running as a systemd process. Sometimes the process takes too much time to come up. This needs to be debugged and may be the etcd version needs to be updated.

[joseph-v]

This PR seems to handle two different features (Ubuntu 20.04 support and Python 2 removal). Can we handle it in separate PRs, so that user can explore all existing features in Ubuntu 20.04?

Ubutnu 20.04 may not have python 2, but there seems to be steps available to install it (Please check: https://linuxconfig.org/install-python-2-on-ubuntu-20-04-focal-fossa-linux)

[joseph-v]

Why do we need all these additional packages?

[anvithks]

@joseph-v As per this install guide we need to install these pacakges.

[anvithks]

This PR seems to handle two different features (Ubuntu 20.04 support and Python 2 removal). Can we handle it in separate PRs, so that user can explore all existing features in Ubuntu 20.04?

Python2 removal is due to the Ansible version upgrade to 2.9.6. They can be separated but there are many dependencies that need to be checked when we install Python2 on ubuntu20.04.
Let me check if I can separate the PRs.

Ubutnu 20.04 may not have python 2, but there seems to be steps available to install it (Please check: https://linuxconfig.org/install-python-2-on-ubuntu-20-04-focal-fossa-linux)

Yes. I will check this link and try out the installation.

[joseph-v]

LGTM