Remove network_host config option

It appears to be unused since 9c0ffe7 and was related to the
stub_network option which itself was removed in 3313cff.

Change-Id: Ic555e3523a90c83c6a89f24619252099c4e55f37
Merge "Remove network_host config option"
Merge remote-tracking branch 'citrix/master' into build-temp