[FS#399] odhcpd: add self configuration for DHCP UCI option 'dns'

[LEDE Bugs]

The following task is now closed:

FS#399 - odhcpd: add self configuration for DHCP UCI option 'dns'
User who did this - Hans Dedecker (dedeckeh)

Reason for closing: Duplicate
Additional comments about closing: Fixed by implementation for FS#635

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=399