LU-12513 utils: add handling YAML_NO_TOKEN

LU-12513 utils: add handling YAML_NO_TOKEN

YAML_NO_TOKEN is something that is not a key value pair, either
an entry or exit into a sub-structure. The parser equates it to
an error. This flaw makes a YAML format that is valid be treated
as invalid. Add handling YAML_NO_TOKEN as a valid setting. This
flaw was discovered in the patch for the LU-6081 work.

Test-Parameters: trivial

Change-Id: Ibe0c0a2bea22b26a0dd2d900b7a4a5957b96e3da
Signed-off-by: Ben Evans <bevans@cray.com>
Reviewed-on: https://review.whamcloud.com/35428
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>