Properly clean up temporary files on importer error

[ZetaTwo]

Apr 03 13:30:00 hashr2 bash[1362]: I0403 13:30:00.043981    1362 hashr.go:200] Preprocessing linux-tools-4.15.0-106-generic_4.15.0-106.107_amd64.deb
Apr 03 13:30:00 hashr2 bash[1362]: I0403 13:30:00.044380    1362 common.go:142] Copying linux-tools-4.15.0-106-generic_4.15.0-106.107_amd64.deb to /tmp/hashr-linux-tools-4.15.0-106-generic_4.15.0-106.107_amd64.deb-309297636/linux-tools-4.15.0-106-generic_4.15.0-106.107_amd64.deb
Apr 03 13:30:00 hashr2 bash[1362]: E0403 13:30:00.045723    1362 hashr.go:308] deb: skipping source linux-tools-4.15.0-101-generic_4.15.0-101.102_amd64.deb: error while preprocessing: error while opening tar archive in deb package: xz: data is truncated or corrupt
Apr 03 13:30:00 hashr2 bash[1362]: I0403 13:30:00.046763    1362 hashr.go:233] Deleting

The "Deleting" log line is missing a path

hashr/core/hashr/hashr.go

Line 233 in 8c20ba5

glog.Infof("Deleting %s", path)

which is probably also why the removal never happens. This could have been dangerous as well considering the command below is "sudo rm -rf ".