bump smoke tests to xenial, increase RAM
bump smoke tests to xenial, increase RAM

started seeing this error, so let's give it more:

    {"timestamp":"1533673123.163292885","source":"baggageclaim","message":"baggageclaim.api.volume-server.stream-out.failed-to-stream-out","log_level":2,"data":{"error":"fork/exec /bin/tar: cannot allocate memory","session":"6.1.41","volume":"4abd788f-2fba-4228-7556-d26146d345be"}}

concourse/pipelines