allow use of self-signed certificates with influxdb

[rotanid]

it would be nice to be able to allow self-signed certificates for the database connectors like influxdb

Expected Behavior

the connection should simply work

Current Behavior

there's a panic because of the self-signed certificate

Possible Solution

allow self-signed certificates either by default or by choice

Context

connection to influxdb should be encrypted, without the need for some "official" CA

Your Environment

influxdb 1.5.x
yanic current (what is installed by go get -v -u github.com/FreifunkBremen/yanic)

[corny]

I would like to see an option to reference the root certificate.