Unbreak tests that use mapped addresses on bionic.

On bionic, creating an IPv4 packet where the destination address
is an IPv4-mapped address such as "::ffff:8.8.8.8" fails. This
appears to be because unlike glibc, bionic's getaddrinfo does not
convert mapped addresses into IPv4 addresses when ai_famil is
AF_INET.

Fix this by correctly only passing in proper IPv4 addresses.
Attempt to make this clear by clearly separating addresses from
socket addresses.

Bug: 36510518
Test: multinetwork_test, sock_diag_test, and most of xfrm_test pass on walleye
Test: all_tests.sh passes on android-4.9
Change-Id: I3b8e06bd1f808f80981a60175c5d350948bb7675