RAPI: Make node evacuation actually work

Commit e1f23243 changed te LU and opcode for node evacuation to receive
a “mode” parameter (among other things). Commit de40437a changed the
RAPI code accordingly, but did so for an earlier version of the first
patch. Obviously this couldn't work, so here's the fix.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>