[Telemetry] Adding Erno Kuvaja (jokke_) to telemetry cores

Hi there,

a bit premature, but in-line with[1] I've added Erno to telemetry cores.

Erno is not a stranger in the OpenStack world and has been deeply involved in glance for quite a while. Thank you Erno for stepping up and for helping with Telemetry!

Matthias

[1] https://governance.openstack.org/election/#ptl-candidates