Find and select the machine token on drop

* New method to find a machine or container token given the machine's name
* Update call sites to select the machine/container token on creation.
* Tests.
I'm going to agree with @kadams54 here. Both of the branches of the conditional are identical save for the boolean value. If you put that indexof check in that fn then you can remove this check entirely and remove the param from the fn for the call on line 414 above. 

It also seems like everywhere the `_findMachineOrContainerToken` is called then the `_selectMachineToken` is also called. What do you think of renaming `_findMachineOrContainerToken` and placing the `_selectMachineToken` call into this fn?