Change blob reader in test to satisfy travis
Change blob reader in test to satisfy travis

Looks like travis is using different version of tar that
fails to detect file presence in tarball

Signed-off-by: Phan Le <f2c5995718b197bbd6f63c99e8aab6ee2af1c495@pivotallabs.com>

forrestsill/bosh-init,cloudfoundry/bosh-init,allomov/bosh-init,cloudfoundry/bosh-init,forrestsill/bosh-init,allomov/bosh-init,forrestsill/bosh-init,allomov/bosh-init,cloudfoundry/bosh-init