Remove IF NOT EXISTS from create database command
The `IF NOT EXISTS` syntax has been removed from Influxdb v1.0.0
onwards. Ref:
# DDL
CREATE USER fluo WITH PASSWORD 'secret' WITH ALL PRIVILEGES
-CREATE DATABASE IF NOT EXISTS fluo_metrics
+CREATE DATABASE fluo_metrics
CREATE RETENTION POLICY r3d ON fluo_metrics DURATION 3d REPLICATION 1 DEFAULT
CREATE RETENTION POLICY r3m ON fluo_metrics DURATION 12w REPLICATION 1
