adb: don't try to resolve 'localhost'

Misconfigured systems can have localhost pointing to an address that
isn't 127.0.0.1 or ::1.

adb is the only caller of the libcutils socket_loopback functions, so
move them into adb and switch the implementations over to using
INADDR_LOOPBACK and in6addr_loopback, instead of resolving 'localhost'
when connecting.

Bug: http://b/37282612
Test: `killall adb; adb shell`
Test: `killall adb; ip addr del 127.0.0.1/8 dev lo; adb shell`
Change-Id: I01c1885f1d9757ad0f7b353dd04b4d1f057741c8
7 files changed