For OS X, compute checksum for IPv4 SOCK_DGRAM sockets as well. (#539)
For OS X, compute checksum for IPv4 SOCK_DGRAM sockets as well. (#539)

Darwin kernel never seems to compute checksum for IPv4.

Fixes: https://github.com/google/cloudprober/issues/537
PiperOrigin-RevId: 348598094
cloudprober/cloudprober,cloudprober/cloudprober,google/cloudprober,google/cloudprober,cloudprober/cloudprober