[3221] Addressed review comments.

Made behavior of dhcp_ddns::WatchSocket a bit more robust in handling
programmatic abuse.
Cleaned up addresses used in ncr_upd_unittest.cc, added specific test
for client side address if 0.0.0.0/port 0.
Updated copyrights as appropriate and other cosmetics.
[3221] Fixed doxygen errors, removed commented include

Fixed a couple doxgyen errors and removed the commented
out include of ioctl.h in d2_upd_unittest.cc
[3221] Improved WatchSocket error handling in dhcp_ddns::NameChangeUDPSender

Shored up the error handling in the sender when the WatchSocket fails to mark
or clear. Addes unit tests accordingly.
[3221] Corrected typo and spelling in new log message

Also ran dhcp_ddns_messages.mes through reorder tool.