added initial implementation of code to detach EBS volumes
Merge remote-tracking branch 'org/testing' into use-persistent-disks-in-aws
checking to see if EBS volumes exist before using them in EC2
added error handling on instance detaching, and detaching from sdc instead of sdb
added abstract method in base_agent, to keep interface up to date with implementors
merged with specify-zone-as-flag
Merge remote-tracking branch 'org/testing' into use-persistent-disks-in-aws
Merge pull request #290 from shatterednirvana/use-persistent-disks-in-aws

Use EBS volumes in AWS to persist data