Update cloud-init-per Logic for compatibility with 7.6

[ferricoxide]

Problem Description:

With EL 7.6's rebasing of cloud-init, the current cloud-init-per declaration in UserData results in the secondary EBS being mkfsed each time the instance boots.

Expected Behavior:

Secondary EBS is only mkfsed during initial boot

Actual Behavior:

Secondary EBS being mkfsed each time the instance boots.

Fix recommendation:

Update UserData. Change:

"  - cloud-init-per instance mkfs-appvolume mkfs -t ext4 ",

To:

"  - cloud-init-per instance appvolume mkfs -t ext4 ",