Changes

socket.h: Include netinet/in.h instead of arpa/inet.h

In socket.h we are mainly interested in netinet/int.h, since that's the
one defining INET_ADDRSTRLEN, struct sockaddr_in, struct in_addr, ec.

Header arpa/inet.h usually defines several functions which use those,
like htonl(), inet_ntop(), etc.

See POSIX:
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/arpa_inet.h.html#tag_13_03
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/netinet_in.h.html

Change-Id: I03919c4adc962bbcfabc9030c6f12c0e10ff060c