only find ebs snapshots that have completed
only find ebs snapshots that have completed

because attempting to attach a snapshot in a "pending" state is silly

scalp42/aws,paybyphone/aws,opscode-cookbooks/aws,BuyerQuest/aws,xacaxulu/aws,joshoohaah/aws,TheWeatherCompany/aws,udomsak/aws,Altiscale/aws,rafaelfelix/aws,localytics/aws,miketheman/aws-cookbook,strebitz/aws,evertrue/aws,needle-cookbooks/chef-opscode-aws,ForeverOceans/aws,arnaud036/aws,chef-cookbooks/aws,incent-corp/aws,Tealium/aws,itwasntandy/aws,grosendorf/aws