Deduplify TrailingZero and LeadingZero linters

Perhaps a silly change, but our CodeClimate score is being affected by
the apparent duplication in these two classes. Rename some variables to
see if we can fix that.

Change-Id: I3ea6eaa016a954ee745e893a5ff325bdaae9af15
Reviewed-on: http://gerrit.causes.com/44954
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>