gpg: Make --auto-key-locate work again with keyservers.
* dirmngr/ks-engine-hkp.c (ks_hkp_get): Allow exact search mode. * g10/keyserver.c (keyserver_import_name): Implement. (keyserver_get): Use exact mode for name based import. (keyserver_get): Add args R_FPR and R_FPRLEN. Change all callers.