Remove fallback dynamic engine loading support.

Remove fallback dynamic engine loading support.

Since we no longer have dynamic engines, don't bother falling back to them
if a builtin engine is not found first.

Before:

$ openssl dgst -engine unknown
invalid engine "unknown"
27256010481532:error:2606A074:engine routines:ENGINE_by_id:no such
engine:/usr/src/lib/libcrypto/crypto/../../libssl/src/crypto/engine/eng_list.c:384:id=unknown
27256010481532:error:2606A074:engine routines:ENGINE_by_id:no such
engine:/usr/src/lib/libcrypto/crypto/../../libssl/src/crypto/engine/eng_list.c:384:id=dynamic

After:

$ openssl dgst -engine unknown
invalid engine "unknown"
27256010481532:error:2606A074:engine routines:ENGINE_by_id:no such
engine:/usr/src/lib/libcrypto/crypto/../../libssl/src/crypto/engine/eng_list.c:384:id=unknown

ok doug@