Why is attempted upgarde of the RHEV Manager from 3.0 to 3.1 failing with the following error: "Host (IP), reason: no BIOS UUID?"

Issue

• While upgrading from RHEV 3.0 to RHEV 3.1 the following error was encountered.

During the upgrade process, RHEV Manager  will not be accessible.
All existing running virtual machines will continue but you will not be able to
start or stop any new virtual machines during the process.

Would you like to proceed? (yes|no): yes
Stopping ovirt-engine service...                         [ DONE ]
Stopping DB related services...                          [ DONE ]
Pre-upgrade validations...                               [ ERROR ]
Pre-upgrade host UUID validation failed

Please move the following hosts to maintenance mode before upgrade:
   - Host (IP), reason: no BIOS UUID