Allow EC2 image registration using /dev/sda1 device name - EUCA-7167

Image registration now allows use of the (default) /dev/sda1 device
name. When this device is used, and there is no mapping for the /dev/sda
device, we will accept the registration and map the device name to
/dev/sda.

EUCA-7167
Merge origin/dev/sjones/EUCA-7167 to testing
Merge branch 'dev/sjones/EUCA-7167_merge' into testing