Public key not available for influxdb

[dwkim922]

The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D8FF8E1F7DF8B07E
Error message shows up when running vagrant up for the first time.

It looks like it failes on line 23 sudo apt-get update && sudo apt-get install -y influxdb failing to install influxdb.

I manually added sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys D8FF8E1F7DF8B07E before apt-get install and it seems to work fine. (requested pull request with this applied)

This is a temporary fix so I think the line 23 needs to be reviewed.

Thanks