[krbdev.mit.edu #6404] kdb5_ldap_util broken by virtualization of krb5_dbekd_encrypt_key_data

[Greg Hudson via RT]

The merge of Luke's code in r21690 changed krb5_dbekd_encrypt_key_data
into a virtual function indirecting through lib_handle.  This breaks
kdb_ldap_util, which uses a dal_handle with a NULL lib_handle and makes
direct calls to libkdb_ldap and (formerly) non-virtual functions in
libkdb.  The reason for using this faked-up dal_handle is that there is
possibly no valid LDAP back end to open.

Sam's opinion is that the best fix is to expose kdb_setup_lib_handle,
thus allowing kdb5_util to set up a dal_handle with a valid lib_handle
(and then fill in the db_context itself, as it does now).

There is also the option of using a krb5_db_create or krb5_db_open
depending on the kdap_ldap_util operation, and adjust the code accordingly.