Clear dirty subsystem for hosts and staticmaps when unbound is enabled
Take unbound into consideration when creating /etc/hosts, also use new unbound parameters for dhcpleases when it's necessary, helps ticket #4011
Unbound improvements and fixes, ticket #4011:

- Create dhcpleases_entries.conf, feed by dhcpleases
- Do not read lines created by dhcpleases from /etc/hosts to populate
host_entries.conf
- Simplify logic for host_entries.conf creation