do not run telemetry integration on xenial
do not run telemetry integration on xenial

gnocchi stable/2.1 is mapped to stable/mitaka. i enabled trusty
gate to run in I2f10e03c798943f6035bdd795cf3ea9f89e4d582. this patch
attempts to disable the xenial job.

Change-Id: Ib8f80f31245deec685f3a7ce98da9a6b04179369

openstack-infra/project-config,openstack-infra/project-config