When running in a container using overlayfs we may see the following
warning:
WARNING os_brick.initiator.connectors.nvmeof process execution error
in _get_host_uuid: Unexpected error while running command.
Command: blkid overlay -s UUID -o value
Exit code: 2
Stdout: ''
Stderr: '': oslo_concurrency.processutils.ProcessExecutionError:
Unexpected error while running command.
This change fixes the issue by not running the command when the file
system source is overlay.
Closes-Bug: #2045557
Change-Id: I3abc5bee7f474a9a40d396c559a42edff86334e0
(cherry picked from commit bd07c571da7a3f78dbdec68af638b7e16181848d)