Regression: HttpSeverOperations overrides content-length to 0 on HTTP HEAD #171

Original Issue: https://github.com/reactor/reactor-netty/issues/171
Regression is caused by the fix provided for `Transfer-Encoding & Content-Length headers are being sent in response headers.` #1153 
https://github.com/reactor/reactor-netty/commit/317355f66edefaf48d4f09f3727c57b03fe73a3d

Reactor-Netty: version: 0.9.11.RELEASE