update loxigen-artifacts

* submodules/loxigen-artifacts 2bdcfd8...515fac2 (1):
  > Artifacts from https://github.com/floodlight/loxigen/compare/764a45f513b0d48abb71813ea89124829221d319...0ab7418dde3e00917b816fce5968c44d768a270d
Merge into master from pull request #119:
update loxigen-artifacts (https://github.com/floodlight/ivs/pull/119)