Key identifier is assumed to have a specific format despite warning in spec

[xurtis]

Describe the bug

The key info is parsed to obtain a key grip and fails for key descriptions that don't conform to the format. The pinentry documentation states that the key identifier must be considered opaque.

Although --clear may be passed here for unidentified keys, they should not set the allow-external-password-cache option and the key identifier shouldn't be mapped to any cache.