[202311][counter] Clear counter table when dhcpmon init (#14)

[202311][counter] Clear counter table when dhcpmon init (#14)

Cherry-pick from #14

Why I did it
Fix issue sonic-net/sonic-buildimage#15047
dhcp counter didn't restore after config reload

Work item tracking
Microsoft ADO (number only): 26270786
How I did it
Clear all counters when dhcpmon start
Remove clear counter in initialize_counter since they are cleared in previous
How to verify it
Build debian packet and install in DUT do manually testing
Run dhcp_relay test, all passed

Signed-off-by: Yaqiang Zhu <[email protected]>