Remove version check for Overcommit < 0.6.0

This version is old enough that it can safely be ignored, allowing us to
simplify the main script.

Change-Id: Ie4c6b8f8b64ac487f29b1e56c9532094b7a33824
Reviewed-on: http://gerrit.causes.com/45334
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>