bump diego-stress-tests
bump diego-stress-tests

[delivers #145146609]

Submodule src/code.cloudfoundry.org/diego-stress-tests 78bdeba..175e932:
  > drd monitors BBS events and streams JSON output on any changes

Signed-off-by: Nima Kaviani <0ebde517669f70c2aec92dc89d4950413b825ec0@us.ibm.com>

cloudfoundry-incubator/diego-perf-release,cloudfoundry-incubator/diego-perf-release