Centos 6.6 yum issues with NTP update

You're seeing this because a previous yum transaction, which was attempting to update ntp, was interrupted partway through. You're generally warned the next time you try to use yum, that you need to run yum-complete-transaction, but you may only be warned once. If you ignore the warning, you end up in this situation.

To resolve the problem, use the package-cleanup utility.

package-cleanup --dupes

shows duplicate packages (the problem here)

package-cleanup --cleandupes

removes the duplicates. You may want to yum reinstall the affected packages to be 100% sure.

package-cleanup --problems

will show you any other problems with the RPM database.