[CI] Update to nginx for CI instead of http server

[SanjalKatiyar]

#854 >> reverted to ODF 4.13 as current 4.14 (which corresponds to master) has some issues.
To make ODF 4.13 work had to revert back to http server as well because ODF 4.13 do not have privileges config to work with "nginx-unprivileged" (was added for 4.14 only).

Once we move to ODF 4.14 for CI, we need to move back to nginx as well.