Only skip platform tests if creating a platform throws GEOPM_ERROR_PLATFORM_UNSUPPORTED.
Only skip platform tests if creating a platform throws GEOPM_ERROR_PLATFORM_UNSUPPORTED.

- In other cases warning message is printed, by
  geopm_platform_supported but return code is zero.

Change-Id: Id4eaaeaca2d92ad17463eeaa9ad86507594f9e90
Signed-off-by: Christopher M. Cantalupo <9cf3ecca60a3dd7112ab0e7250bedb8a752e3958@intel.com>

cmcantalupo/geopm,cmcantalupo/geopm,cmcantalupo/geopm,sssylvester/geopm,sssylvester/geopm,geopm/geopm,cmcantalupo/geopm,geopm/geopm,cmcantalupo/geopm,sssylvester/geopm,geopm/geopm,sssylvester/geopm,geopm/geopm,geopm/geopm