Re-implement OS-specific bits from default_gateway, add OpenBSD-support while here
Re-implement OS-specific bits from default_gateway, add OpenBSD-support while here

higanworks/specinfra,RoboticCheese/specinfra,pfaffle/specinfra,mizzy/specinfra,elibus/specinfra,lurdan/specinfra,miketheman/specinfra,stoned/specinfra,k0kubun/specinfra,sorah/specinfra,verisign/specinfra,optimizely/specinfra,edolnx/specinfra,uroesch/specinfra,tacahilo/specinfra,chorrell/specinfra,chef-partners/specinfra-cisco,glenux/contrib-specinfra,gh2k/specinfra,hfm/specinfra,seroron/specinfra,hideyuki/specinfra,skamithi/specinfra,sean-horn/specinfra,winebarrel/specinfra,r7kamura/specinfra,chinthakagodawita/specinfra,thenexus6/specinfra,ihassin/specinfra,minimum2scp/specinfra,mactkg/specinfra,sergueik/specinfra,stefanhorning/specinfra,aibou/specinfra,electrical/specinfra,bodgit/specinfra,serverspec/specinfra,nurse/specinfra