Update prometheus dependencies (#3239)
Update prometheus dependencies (#3239)

This commit updates the following prometheus related dependencies:
* github.com/prometheus/client_golang to v1.1.0
* github.com/prometheus/procfs to v0.0.3 (required by the above)
* github.com/prometheus/common to v0.6.0
* github.com/prometheus/client_model to latest (no releases)

Fixes #3238
Oncilla/scion,Oncilla/scion,netsec-ethz/scion,netsec-ethz/scion,Oncilla/scion,netsec-ethz/scion,netsec-ethz/scion,Oncilla/scion