Trying to put a host into maintenance mode in vCenter and one machine wouldn't VMotion because it said VMware Tools were being installed or upgraded.
Searching Google came up with this article which applies to ESX 4.x:
Well vmware-cmd is gone in ESXi 5.x. Here's how you do it in ESXi 5.x:
Note the VmId of the machine having the issue. Then run:
vim-cmd vmsvc/tools.cancelinstall VmId