The importance of this test is to make sure we go in without a false positive, that we start with a blank slate. If this returns true for some reason, then the subsequent tests would return true as well, but not because of the actual behavior that we're testing.

Also, the other tests won't run if there's a reboot pending, because registry_safe? is in there to ensure we don't muck up the system if there is a real reboot pending. It's not a huge deal with something like Windows Update\Auto Update, but if we modified PendingFileRenameOperations, we would be overwriting important data.

These tests won't work right if there's a reboot pending, because reboot_pending? will return true regardless of our test setup. We raise that with this test failing, and avoid being destructive by using registry_safe? on following tests.