lchan: Avoid applying transition changes if state new==old
lchan: Avoid applying transition changes if state new==old

Let's avoid running over state change conditions or even printing log
lines if there's no state change.

Change-Id: I1ca86aa846084f53751076643665cb6dabc26a06

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts