Bluetooth: Controller: llcp: Fix failing UT for version exchange

Test that verifies correct handling of Version exchanged procedure
called twice on the same connection failed. The reason was wrong
number of expected free procedure context objects. It was expected
that there will be one context not released.
That was wrong because the context is released just after the procedure
completes in idle state. The second and following calls to the procedure
do not start any PDU exchange, so the procedure ends immediately.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>