tahoe create-node writes tcp=tor even for i2p

[dawuud]

str4d has found that even without txtorcon installed you can trigger a bug where configuring a storage node via the CLI doesn't work as expected:

` tahoe create-node --hide-ip --listen=i2p

tahoe create-client --hide-ip --introducer=i2p:... `

these two commands result in the tahoe.cfg being written with:

` [connections] tcp=tor `

the subsequent tahoe start command will of course fail.