It's a small script that makes it easier to connect to a Microdroid VM
running in the Android device.
Usage: vm_shell [cid]
If cid is omitted it displays the CIDs of available VMs and lets you
select one.
Bug: N/A
Test: m vm_shell and run it
Change-Id: I762f1161024d151a2f9e75fdb217037f1f9a1e1d