op-mode: T1375: Allow to clear dhcp-server lease
Allow to reset dhcp-leases per ip
Parse file '/config/dhcpd.leases' find match section 'lease x.x.x.x {}'
And remove this section
clear dhcp-server lease 192.0.2.21
(cherry picked from commit a83eecfeee1f925c914a46623dd35f96b48389f8)