journald: fix fd leak in journal_file_empty

Before my previous patch, journal_file_empty wasn't be called with the
correct filename. Now that it's being called with the correct filename
it leaks file descriptors. This patch closes the file descriptors before
returning.

Signed-off-by: George McCollister <george.mccollister@gmail.com>

[Edit harald@redhat.com: make use of _cleanup_close_ instead]

src/journal/journal-vacuum.c

@@ -129,8 +129,9 @@ static void patch_realtime(
 }
 
 static int journal_file_empty(int dir_fd, const char *name) {
-        int fd, r;
+        int r;
         le64_t n_entries;
+        _cleanup_close_ int fd;
 
         fd = openat(dir_fd, name, O_RDONLY|O_CLOEXEC|O_NOFOLLOW|O_NONBLOCK);
         if (fd < 0)