Avoid leaking file descriptors

Add O_CLOEXEC on open() calls, and SOCK_CLOEXEC on socket calls.
This avoids leaking file descriptors across execs.

Addresses the following SELinux denial:

  audit(1422740213.283:8): avc: denied { read write } for pid=2597 comm="clatd" path="socket:[6709]" dev="sockfs" ino=6709 scontext=u:r:clatd:s0 tcontext=u:r:netd:s0 tclass=netlink_socket

and allows the removal of some other SELinux rules which were
inappropriately added because of leaking file descriptors.

Change-Id: I9c180488ea1969d610e488f967a7276a672bb477
diff --git a/server/NetlinkManager.cpp b/server/NetlinkManager.cpp
index 118a5bd..76af46f 100644
--- a/server/NetlinkManager.cpp
+++ b/server/NetlinkManager.cpp
@@ -76,7 +76,7 @@
     nladdr.nl_pid = getpid();
     nladdr.nl_groups = groups;
 
-    if ((*sock = socket(PF_NETLINK, SOCK_DGRAM, netlinkFamily)) < 0) {
+    if ((*sock = socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, netlinkFamily)) < 0) {
         ALOGE("Unable to create netlink socket: %s", strerror(errno));
         return NULL;
     }