You have a few options. If you want to update just ondemand:
yum update ondemand
If you want to update OS you will have to exclude ondemand:
yum update --disablerepo=ondemand-web
Doing a blanket update will not work at this time due to updates to our latest repo in preparation for building OnDemand 2.0 RPMs. I would strongly recommend not updating to that release at this time because there are numerous breaking changes that we’ve not yet documented. It might be a good idea to switch to OnDemand 1.8 repos for the time being. If you installed repos with RPMs:
yum remove ondemand-release-web-latest
yum install https://yum.osc.edu/ondemand/1.8/ondemand-release-web-1.8-1.noarch.rpm
If you installed repos via some other means just replace latest in URL with 1.8 in the repo file under /etc/yum.repos.d.