By default, VMware Tools are automatically updated when power-cycling a VM each time a new version is available. This may not be desirable, and currently, there is no way to change this behaviour anywhere in the settings. This setting can however by changed manually on a VM-basis, by manually editing the VM's configuration file (.vmx).
Although there's mention of a global setting in Fusion's configuration files, many users report this as not working, so I only mention the per-VM setting here.
Next time you start the VM, and there's an update of VMware Tools, they should no longer update automatically for this particular VM. You can always revert the behaviour by changing the parameter back to its original value.