Openvpnc config cleanup

This change goes with a commensurate change to the elife-vagrant code to enable the VPN to not be setup if needed. 

The recipe now requires node[:elifejnl][:setup_vpn_client] to be set as a boolean value, and the default for this is 'false' so that the VPN is not created by default (which would require that various files were provided).

See also  https://github.com/elifesciences/elife-vagrant/pull/12