"change_controller" refactor

old_controller != new_controller && !was_local && tm.is_local()
is not needed becasue
!was_local && tm.is_local()
already implies
old_controller != new_controller.
comment to assert.
"change_controller" refactor

we don't need to restart the turn if it wasn't local before and isnt
local now.

Also we change the conditional structure which should have no effect on
the resulting code.