Rework all functions in zone_register.c to work with exact match on zone name.
This change allows us to store inactive and active zones in the same zone
register, without a risk that update in inactive zone will change data
in an active zone.
https://fedorahosted.org/bind-dyndb-ldap/ticket/127
Signed-off-by: Petr Spacek <pspacek@redhat.com>