Handle alternative block device path for AWS disk mounts

What does this MR do?

MR tackles a scenario that can occur with AWS Data Disks.

Specifically when a disk is attached to an existing AWS instance it will report the block device path /dev/sdX. For some reason if the disk is attached at the same time as the instance is created, e.g. if you change the instance type, this path changes to just sdX.

This addition will cover both of these scenarios.