Refine expectation for output file sizes
Refine expectation for output file sizes

- `df` will output different sizes for different disk systems because it
  reports disk usage and not strictly disk size

[#127357631]

Signed-off-by: Jacques Chester <8f1e729cbc4d489c19883827c4c21d9fbbde0732@pivotal.io>

cloudfoundry-incubator/buildpack-packager,cloudfoundry/buildpack-packager