ruby: Fix double statistic registration in garnet

ruby: Fix double statistic registration in garnet

Currently garnet will not run due to double statistic registration of new
stats in ClockedObject. This occurs because a temporary array named 'cls'
is being added as a child to garnet internal and external link SimObjects.
This patch simply renames the temporary array which prevents it from
being added as a child object and avoids the assertion that a statistic
was already registered.

Committed by Jason Lowe-Power <jason@lowepower.com>