lttng: Fix error in virtual machine analysis

lttng: Fix error in virtual machine analysis

The analysis was not checking if the virtual cpu was idle
before setting the current state to preempted.
Now it is ignored in this situation.

Change-Id: Iddef5c2ec1c916ea0b591d0106b4e6473febb819
Signed-off-by: Cédric Biancheri <cdc.biancheri@gmail.com>
Reviewed-on: https://git.eclipse.org/r/56728
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-by: Francis Giraldeau <francis.giraldeau@gmail.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>