Exporter blocks drop-database

[zesoup]

Hi,

as the exporter keeps its connection open between scrapes it becomes harder to drop an unused database.

I feel like disconnecting once a scrape is finished serves multiple purposes. It becomes quite obvious for the monitoring once no more connections can be established and as these connections are not permanent it becomes more feasible to use this exporter in a many-database and autodiscovery szenarios. Last but not least there is a DROP DATABASE enhancement as one is currently required to manually remove monitoring connections.

If required i'll provide the patch - would this approach be acceptable?