Close the file handle before exiting the function

When exiting the function because cannot open "oom_adj" file, not close the file handle "dirfd".

BUG=n/a

Review-Url: https://codereview.chromium.org/2419383008
Cr-Commit-Position: refs/heads/master@{#427018}

AUTHORS

@@ -716,6 +716,7 @@ Xuefei Ren <xrenishere@gmail.com>
 Xun Sun <xun.sun@intel.com>
 Yael Aharon <yael.aharon@intel.com>
 Yair Yogev <progame@chromium.org>
+Yan Wang <yan0422.wang@samsung.com>
 Yang Gu <yang.gu@intel.com>
 Yarin Kaul <yarin.kaul@gmail.com>
 Ye Liu <cbakgly@gmail.com>

sandbox/linux/suid/process_util_linux.c

@@ -59,6 +59,7 @@ bool AdjustOOMScore(pid_t process, int score) {
     fd = openat(dirfd, "oom_adj", O_WRONLY);
     if (fd < 0) {
       // Nope, that doesn't work either.
+      close(dirfd);
       return false;
     } else {
       // If we're using the old oom_adj file, the allowed range is now