Kill nginx and blobstore_url_signer when exiting system tests
Kill nginx and blobstore_url_signer when exiting system tests

[#163021331]

Signed-off-by: Peter Goetz <1bf679f6f155949fea19af278a2667a47961da6b@gmail.com>

cloudfoundry-incubator/bits-service-release,cloudfoundry-incubator/bits-service-release,cloudfoundry-incubator/bits-service-release,cloudfoundry-incubator/bits-service-release