Otherwise the function like d.getVarFlag(e, 'task', True) which is used by
do_listtasks will still get it, and list the deleted tasks.
(Bitbake rev: 779d73619daf59f76f5b0313e7fb5409f6e82553)
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>