Don't require chef/rest
Don't require chef/rest

chef/rest does not exist on newer versions of chef. Only require it as
a fallback.

Signed-off-by: Steven Danna <9ce5770b3bb4b2a1d59be2d97e34379cd192299f@chef.io>

chef/opscode-pushy-client,chef/opscode-pushy-client,chef/opscode-pushy-client