macos: no more startupitems

macos: no more startupitems

if we're upgrading, a "cruft" startupitems script should just
be nuked.

FIXES 129601

Reviewed-on: http://gerrit.openafs.org/4387
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 841c8022e3978fffe1357f339d948e93c9db9d52)

Change-Id: Ibe2dde067df1fe22da1bb09039d07ebbc178af08
Reviewed-on: http://gerrit.openafs.org/6277
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>