title: How to delete vagrant snapshots
body: <p>I have ended up having 2 snapshots with same name for a VM in a vagrant multi machine setup. I thought saving again with same name would overrride. Now I want to delete one of them but when I give the name I get </p>
  
  <pre><code>➜  vagrant vagrant snapshot list trusty                  
  my-pkg_1.0
  my-pkg_1.0
  
  ➜  vagrant vagrant snapshot delete trusty  'my-pkg_1.0'
  Progress: 0%There was an error while executing `VBoxManage`, a CLI used by Vagrant
  for controlling VirtualBox. The command and stderr is shown below.
  
  Command: ["snapshot", "11ea7bf9-717c-453d-91e3-4185cec6be92", "delete", "my-pkg_1.0"]
  
  Stderr: VBoxManage: error: Snapshot 'my-pkg_1.0' of the machine 'vagrant_trusty_1482140927350_10789' cannot be deleted, because it is the current snapshot and has one child snapshot
  VBoxManage: error: Details: code VBOX_E_INVALID_OBJECT_STATE (0x80bb0007), component SessionMachine, interface IMachine, callee nsISupports
  VBoxManage: error: Context: "DeleteSnapshot(bstrSnapGuid.raw(), pProgress.asOutParam())" at line 421 of file VBoxManageSnapshot.cpp
  </code></pre>