Use a better random string generator
Use a better random string generator

[#131224155]

Signed-off-by: Alvaro Perez-Shirley <d5000c5ec3097613a224bab22ba8fc2a47fdc5ca@pivotal.io>

cloudfoundry-incubator/cf-test-helpers,cloudfoundry-incubator/cf-test-helpers