add conditional
add conditional

sorta supports Chef 10.x in that it won't blow up, but COOK-4213 will
not be fixed for Chef 10.x by design.

chef-cookbooks/aws,ubiquitousthey/aws,itwasntandy/aws,udomsak/aws,ellongrey/aws,opscode-cookbooks/aws,Tealium/aws,apptentive-engineering/aws,Nordstrom/aws,evertrue/aws,mdellanoce/aws,xacaxulu/aws,simplyadrian/aws,incent-corp/aws,joelmoss/aws,joshoohaah/aws,strebitz/aws,ForeverOceans/aws,localytics/aws,uWhisp/aws,bazbremner/aws,paybyphone/aws,miketheman/aws-cookbook,scalp42/aws,custora/aws,custora/aws,rafaelfelix/aws,TheWeatherCompany/aws,arnaud036/aws,coupa-ops/aws,BuyerQuest/aws,Altiscale/aws,grosendorf/aws,needle-cookbooks/chef-opscode-aws