Fix run_command API
Fix run_command API

This fixes 25e01f562463dcedd1a147260a7638114e39a13d
Due to recent changes, run_command returns the
output of "echo $?" instead of command ouput incase of
success.

So this patch fixes this issue.

Signed-off-by: Pridhiviraj Paidipeddi <fd8ea14509c256cbd04eaa4ee745a213945e70a1@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

open-power/op-test-framework,open-power/op-test-framework,open-power/op-test-framework