Currently we just scp over a tarball from the tester to the SUT as part of a
build target setup without checking to see if one exists. This works if you
always run DTS as the same user, but if multiple different users run DTS
back-to-back the second user will get a failure when trying to copy over the
tarball because scp cannot write over the existing one which the running user
does not own.

This is very easy to fix by simply logging onto the SUT and deleting the
tarball that is already in /tmp, but considering we write DTS under the
expectation that people could run as non-root users, it seems like it could be
worth making a simple quality of life change to make this easier.