Upgrade InfluxDB to 0.12

[baderas]

InflxuDB removed clustering support in the open-source version with their last release (0.12), so actually InfluxDB is stuck at 0.11 in TSDBBench.
See https://influxdata.com/blog/update-on-influxdb-clustering-high-availability-and-monetization/.
InfluxDB Relay (see https://github.com/influxdata/influxdb-relay) can be used to achieve High Availability and could be a replacement for clustering (distribution of data? replication? replication factors?).