healthd: perform periodic chores when awake and on battery power

Monitor battery/charging status at normal awake rate when on battery
power.

Bug: 10650797
Change-Id: I914d24af4963ab9d52b03c0a2615ad653ced9b12
diff --git a/healthd/healthd.cpp b/healthd/healthd.cpp
index 1719c22..9b84c3e 100644
--- a/healthd/healthd.cpp
+++ b/healthd/healthd.cpp
@@ -249,6 +249,9 @@
             if (events[n].data.ptr)
                 (*(void (*)())events[n].data.ptr)();
         }
+
+        if (!nevents)
+            periodic_chores();
     }
 
     return;