Upgrade Rubocop for Travis build from 0.25.0 -> 0.26.0

Fix some new warnings in the process.

Change-Id: I2d4cecc4754f917d4841382a2bf40c2e16eb0f99
Reviewed-on: http://gerrit.causes.com/42249
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>