Clatd changes for move of libipchecksum.

libipchecksum is becoming its own library in
frameworks/libs/net and its include files are no longer under
netutils/. Adjust clatd code accordingly.

Also reorder some include files as suggested by clang-format.

Test: m
Test: atest clatd_test
Test: connects to IPv6-only wifi, testipv4.com shows 10/10
Change-Id: I5e4c73065ce828123aef7e8851227f9bdf444ff9
6 files changed