recovery: Hide unmountable volumes from selection

* In volume manager, check if new volumes are mountable.

* Check volumes for mountable for inclusion into update list.

* Erase unmountable volumes from volumes vector for consistency with
  the item array.

Change-Id: I89ff6cc05a93afffe5e46b24d70fc368bccaf020
diff --git a/volume_manager/VolumeManager.cpp b/volume_manager/VolumeManager.cpp
index 1048061..9a84928 100644
--- a/volume_manager/VolumeManager.cpp
+++ b/volume_manager/VolumeManager.cpp
@@ -136,7 +136,7 @@
 }
 
 VolumeInfo::VolumeInfo(const VolumeBase* vol)
-    : mId(vol->getId()), mLabel(vol->getPartLabel()), mPath(vol->getPath()) {
+    : mId(vol->getId()), mLabel(vol->getPartLabel()), mPath(vol->getPath()), mMountable(vol->isMountable()) {
     // Empty
 }