InfluxDBStore: do not use deprecated "IF NOT EXISTS" condition when creating DB
InfluxDBStore: do not use deprecated "IF NOT EXISTS" condition when creating DB

`IF NOT EXIST` is the default and only behavior (see [InfluxDB issue here](https://github.com/influxdata/influxdb/issues/5707)),
confirmed working locally.

bg451/appdash,bg451/appdash,bg451/appdash