[krbdev.mit.edu #8295] kdb5_ldap_stash_service_password() stash file logic needs tweaking

[Will Fiveash via RT]

In kdb5_ldap_stash_service_password() there is a call to
profile_get_string() at line 127 which is:

        profile_get_string (util_context->profile, KDB_MODULE_SECTION,
section,
                            "ldap_service_password_file", NULL, &file_name);

The problem with this code is that if one has a [dbmodules] section in
krb5.conf but it doesn't contain an assignment for
ldap_service_password_file then file_name ends up being NULL and the
kdb5_ldap_util stashsrvpw command fails with a Failed to open file
error.  The code at line 127 should be:

        profile_get_string (util_context->profile, KDB_MODULE_SECTION,
section,
                            "ldap_service_password_file",
                            DEF_SERVICE_PASSWD_FILE, &file_name);
                            ^^^^^ this as the default value instead of NULL