vold: Fix uninitialized mountpoint bug

Signed-off-by: San Mehat <san@google.com>
diff --git a/VolumeManager.cpp b/VolumeManager.cpp
index d4dad22..a1323ed 100644
--- a/VolumeManager.cpp
+++ b/VolumeManager.cpp
@@ -416,6 +416,7 @@
     char mountPoint[255];
 
     snprintf(asecFileName, sizeof(asecFileName), "%s/%s.asec", Volume::SEC_ASECDIR, id);
+    snprintf(mountPoint, sizeof(mountPoint), "%s/%s", Volume::ASECDIR, id);
 
     if (isMountpointMounted(mountPoint)) {
         LOGD("Unmounting container before destroy");