drbd: Killed an assert that is no longer valid

The point is that drbd_disconnect() can be called with a cstate of
WFConnection.

That happens if the user issues "drbdsetup disconnect" while the
drbd_connect() function executes. Then drbdd_init() will call
drbdd(), which in turn will return without receiving any
packets. Then drbdd_init() will end up calling drbd_disconnect()
with a cstate of WFConnection.

Bottom line: This assertion is wrong as it is, and we do not
see value in fixing it. => Removing it.

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