Use main thread for Binder transactions.

Make the main thread do something useful instead of sitting around
twiddling its thumbs.

Test: builds, boots
Bug: 67041047
Change-Id: I88f7f4fe151ae2b81f80aa575530c12b56ba4d75
diff --git a/main.cpp b/main.cpp
index cca738e..01a2168 100644
--- a/main.cpp
+++ b/main.cpp
@@ -130,12 +130,9 @@
 
     ATRACE_END();
 
-    // Eventually we'll become the monitoring thread
-    while(1) {
-        pause();
-    }
+    android::IPCThreadState::self()->joinThreadPool();
+    LOG(INFO) << "vold shutting down";
 
-    LOG(ERROR) << "Vold exiting";
     exit(0);
 }