Some fixes related to the connection check
The goal of this merge request is to make the conncheck code a bit more readable, and to fix a couple of details in component state transition. More details are given in each commit message:
- 6bbeba27 and ecc1c42f fix two minor problems in the component state transition connected <--> ready
- 263c0903 updates the code to not change the pair state, when it is put on the triggered check list.
- d63c7159 clears the retransmit flag when the stun transaction list is removed from its last element.