Remove unnecessary protocols from TLS ALPN offering

Andreas Schulze reported that NSD's TLS implementation offers these protocols:
`ALPN/HTTP2 h2, spdy/3.1, http/1.1, grpc-exp, h2-fb, spdy/1, spdy/2, spdy/3, stun.turn, stun.nat-discovery, webrtc, c-webrtc, ftp (offered)`

But as we don't do HTTPS they are unnecessary.
