Augment the auto-loadvm behaviour with corresponding auto-savevm-on-exit behaviour.

Autosave fires when loadvm would have been tried - whether it succeeded or not - in
order to bootstrap from an empty snapshot file.

 - New autosave behaviour inhibited with -no_snapshot_save flag.
 - Underlying behaviour implemented with a new qemu option -savevm_on_exit

Change-Id: If64d89f004565ecbb431bc7e96ecc37e27876d67
diff --git a/android/cmdline-options.h b/android/cmdline-options.h
index 1ae3121..3aaa478 100644
--- a/android/cmdline-options.h
+++ b/android/cmdline-options.h
@@ -81,6 +81,7 @@
 OPT_FLAG ( no_snapstorage, "do not mount a snapshot storage file (this disables all snapshot functionality)" )
 OPT_PARAM( snapshot,       "<name>", "immediately load state snapshot rather than doing a full boot (default 'default-boot')" )
 OPT_FLAG ( no_snapshot,    "do not start from snapshot, but perform a full boot sequence" )
+OPT_FLAG ( no_snapshot_save, "do not preserve snapshot, if restore was attempted" )
 OPT_FLAG ( snapshot_list,  "show a list of available snapshots" )
 #endif
 OPT_FLAG ( wipe_data, "reset the use data image (copy it from initdata)" )