Introduce fwmarkd: a service to set the fwmark of sockets.

(cherry picked from commit 7d51096d4106a441a15741592d9ccdd0bfaca907)

Change-Id: Ib6198e19dbc306521a26fcecfdf6e8424d163fc9
diff --git a/file_contexts b/file_contexts
index 0926d74..74c6db3 100644
--- a/file_contexts
+++ b/file_contexts
@@ -79,6 +79,7 @@
 /dev/socket/adbd	u:object_r:adbd_socket:s0
 /dev/socket/dnsproxyd	u:object_r:dnsproxyd_socket:s0
 /dev/socket/dumpstate	u:object_r:dumpstate_socket:s0
+/dev/socket/fwmarkd	u:object_r:fwmarkd_socket:s0
 /dev/socket/gps		u:object_r:gps_socket:s0
 /dev/socket/installd	u:object_r:installd_socket:s0
 /dev/socket/lmkd        u:object_r:lmkd_socket:s0