Suspending instance will not update resource usage

As reported in the bug, "memory and vCPUs NOT become available to
create other instances when suspending instance". So update the
description for ' Suspend and resume an instance'.

Change-Id: I4c11c73fe9ba42e77c86cefe4360ce2496e810e1
Closes-bug: #1402502
Merge "Suspending instance will not update resource usage"