This allows NetworkDiagnostics to send ping packets from specific
source addresses in order to detect reachability problems on the
reverse path.

This addresses the following denial:

[  209.744636] type=1400 audit(1441805730.510:14): avc: denied { node_bind } for pid=8347 comm="Thread-202" saddr=2400:xxxx:xxxx:xxxx:40b1:7e:a1d7:b3ae scontext=u:r:system_server:s0 tcontext=u:object_r:node:s0 tclass=rawip_socket permissive=0

Bug: 23661687

(cherry picked from commit c3712143)

Change-Id: Ia93c14bc7fec17e2622e1b48bfbf591029d84be2