Causes an unnecessary exception

it's unused and has a netid property with name different than key
that would cause issues in the next commit

currently it takes 100ms+ to determine the default pool every time,
including subprocess spawning (!), which is unacceptable since
finding out the default value of properties should be instantaneous

instead of checking every thin pool to see if the root device is in
it, find and cache the name of the root device thin pool and see if
there is a configured pool with that name

…dom0-pool00