libcutils: only change cgroup when fd is initialized [ DO NOT MERGE ]

This is to avoid failues on setting non-exist cgroup

Bug: 34193533
Test: on marlin
Change-Id: I619dcba332fda9ec421df811745cf10311beddd3
(cherry picked from commit e46aae2)

libcutils/sched_policy.c

@@ -404,7 +404,7 @@ int set_sched_policy(int tid, SchedPolicy policy)
         }
 
 
-        if (add_tid_to_cgroup(tid, fd) != 0) {
+        if (fd > 0 && add_tid_to_cgroup(tid, fd) != 0) {
             if (errno != ESRCH && errno != ENOENT)
                 return -errno;
         }