DO NOT MERGE:Add missing SOCK_CLOEXEC flag when opening socket

Go through the code that opens socket in marshmallow, and backport the
SOCK_CLOEXEC usage for AF_NETLINK. In kitkat, SOCK_CLOEXEC is not defined;
therefore I used O_CLOEXEC instead.
Bug: 31242981
Test: mma

Change-Id: I792024c16b84ba3d6666d3df6002c89e0028f4b0