installer/oom: Changes for Helm v3 support:

 * Adjust helm invocations based on helm version
 * Use onap/oom/readiness image instead of oomk8s/readiness-check
 * Pin ansible version in test-requirements.txt

These changes are backwards-compatible with Helm v2.

Signed-off-by: Cian Johnston <cian.johnston@est.tech>
Change-Id: I9406e40aa6f7201bfad0756e1020094b86e1dbfc
Depends-On: I86772879458a20426d1c57b092f47e49a56dabce
5 files changed