gpg invocation discards stderr and leaves tempfiles behind

[vchepkov]

The following change https://github.com/voxpupuli/hiera-eyaml-gpg/commit/2681e995ee07636730892d2942775be5310286ab#diff-8f7a8cbc7701c45f0dbf2ab3b622433dd6cb94672da8eb7c6ea0f1bcf7b1ad5e causes problems with debuging gpg issues, since stderr is discarded, also, it leaves tmpfiles behind, since unlink is not called