uefi: only check for key existence in local key mode

When the key is a pkcs11 key, we shouldn't check for the existence
of the private key on disk.

BUG=b:372702794
TEST=Manual

Change-Id: Icf0097c9dfd7b36a40581f19c6066f2a3c0309a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/6180557
Tested-by: Benjamin Shai <[email protected]>
Commit-Queue: Benjamin Shai <[email protected]>
Reviewed-by: Madeleine Hardt <[email protected]>
Reviewed-by: Nicholas Bishop <[email protected]>
1 file changed