Added ISO prefix to match PXE output dest type

[didacog]

Disaster Recovery Linux Manager (DRLM) Pull Request Template

Please fill in the following items before submitting a new Pull Request:

PR details:

• PR type (Bug Fixing / New Feature / Enhancement / Other?): Bug Fixing
• Reference to related issue (issue link):
• Impact (Low / High / Critical / Urgent): Low
• Did you test this PR? yes
• Brief description of the changes in this PR: Change default OUTPUT_PREFIX of ISO to match PXE style OUTPUT dests.