gpg: Fix possible double free in import_revoke_cert.
* g10/import.c (import_revoke_cert): Fix possible double free. Use LEAVE label on errors.
There was a possible double free by calling keydb_release twice, once
before jumping to "leave:" and once after.
Always jump to "leave:" on errors.
- Reported-by: Dirk Mueller
- Fixes-commit: 9e0e5547d2a008332873a9b632f82f9414ad887f
- GnuPG-bug-id: T8328