Lock while partitioning.

Otherwise we get really excited and trip over ourselves while
partitions are still being created.

Bug: 19993667
Change-Id: I034e56b3063a71d73f9311a945c05ea2ae255f7d
diff --git a/VolumeManager.cpp b/VolumeManager.cpp
index 86e3fd4..dcadd14 100644
--- a/VolumeManager.cpp
+++ b/VolumeManager.cpp
@@ -310,6 +310,7 @@
         break;
     }
     case NetlinkEvent::Action::kChange: {
+        LOG(DEBUG) << "Disk at " << major << ":" << minor << " changed";
         for (auto disk : mDisks) {
             if (disk->getDevice() == device) {
                 disk->readMetadata();