[CLATJ#13] ClatCoordinator: open raw socket

Move the raw socket initialization from netd to mainline because
mainline module is going to launch clatd. Need to provide raw
socket for writing local 464xlat IPv6 packets.

Bug: 212345928
Test: flash and boot
Run "atest ClatCoordinatorTest" in a followup commit.

Change-Id: I6d1da4f1b400eeed87771ae8197b0c58ec50804b
2 files changed