Properly call closedir() in top.cc

This was causing a memory leak when using top with the flag to query all
PIDs (the issue did not affect starter, as starter is only querying
known PIDs).

Change-Id: Ib0e8d3c24f9e68522a4e89f6143ce1004634107a
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/util/top.cc b/aos/util/top.cc
index 9a6bbd0..79ee2db 100644
--- a/aos/util/top.cc
+++ b/aos/util/top.cc
@@ -172,6 +172,7 @@
         pids.insert(pid);
       }
     }
+    closedir(dir);
   }
 
   for (const pid_t pid : pids) {