added a describe_volumes function
Merge branch 'salt-cloud_ec2_describe_volumes' of github.com:Katafalkas/salt into salt-cloud_ec2_describe_volumes
show_volumes is now a wrapper for describe_volumes and slight mods to describe_volumes
describe_snapshots change to non-plural fix
Merge pull request #12598 from Katafalkas/salt-cloud_ec2_describe_volumes

describe_volumes function