drbd: Fixed logging of old connection state

During a disconnect the oc variable in _conn_request_state()
could become outdated. Determin the common old state after
sleeping.
While at it, I implemented that for all parts of the state

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>