Add missing DNS view attach/detach to LDAP instance management code.
    This fixes race condition in BIND shutdown after SIGINT:
    - failing assert caused by use-after-free in dns_zt_find():
    (((zt) != ((void *)0)) && (((const isc__magic_t *)(zt))->magic
    == ((('Z') << 24 | ('T') << 16 | ('b') << 8 | ('l')))))
    
    Signed-off-by: Petr Spacek <pspacek@redhat.com>