Bluetooth: Mesh: Return ETIMEDOUT if k_sem_take call times out

EAGAIN is used in some other places in the code, e.g. if node is not
provisioned when a model tries to send a message. This change helps to
differentiated if the acknowledged message timed out from other failers.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>