Simplify the code in the hostname resource
Simplify the code in the hostname resource

Use the darwin? helper instead of looking for a binary that only exists on darwin
Remove the declare_resource usage we don't need anymore

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

chef/chef,gene1wood/chef,nvwls/chef,mwrock/chef,mwrock/chef,MsysTechnologiesllc/chef,MsysTechnologiesllc/chef,mattray/chef,nvwls/chef,chef/chef,mattray/chef,gene1wood/chef,mwrock/chef,gene1wood/chef,tas50/chef-1,mwrock/chef,gene1wood/chef,tas50/chef-1,tas50/chef-1,tas50/chef-1,chef/chef,MsysTechnologiesllc/chef,chef/chef,mattray/chef,nvwls/chef,mattray/chef,nvwls/chef,mattray/chef,nvwls/chef,nvwls/chef,MsysTechnologiesllc/chef