Backport fix for keytotpm
Backport https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=commitdiff;h=9909f622f69e2b5775099931406dce2d35011281 from STABLE-BRANCH-2-4.
Without this patch, keytotpm
fails with:
gpg-agent: updating regular key file '/path/to/.gnupg/private-keys-v1.d/FINGERPRINT.key' by a shadow key inhibited