[wperf] WPERF-1261: disable CMN-S3 completely if isolated nodes are not defined with wperf.ini

Introduction

This patch depends on series of patches for WPERF-1261, see

• [wperf,wperf-test] WPERF-1261: load CMN isolati... (!1029 - merged),
• [docs,wperf] WPERF-1261: Update CMN.md and READ... (!1030 - merged) and
• [wperf] WPERF-1261: limit number of isolated CM... (!1031 - merged).

In this patch we are disabling CMN completely if CMN-S3 wperf.ini file with isolated nodes is not present and not configured completely.

In this patch:

• wperf: add warning when we disable CMN-S3 from non-isolated configurations
• wperf: only allow CMN-S3 detection and use if 'wperf.ini' file is defined