Demote HTTP proxy errors to warnings
Demote HTTP proxy errors to warnings

These can happen if the client misbehaves, which is not an error
in the proxy itself.

Signed-off-by: David Scott <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@recoil.org>

djs55/vpnkit,djs55/vpnkit,djs55/vpnkit