macos avoid dotunderbar lookups in fakestat mode

macos avoid dotunderbar lookups in fakestat mode

cocoa tries to lookup ._ files for every object, possibly generating
AFSDB queries and other fun. avoid them

Change-Id: Id70b6335d4dddcb6d5628a9883b2c81193bb39d7
Reviewed-on: http://gerrit.openafs.org/896
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 019ae5240691f27beaf583084fc81f4efb84b166)
Reviewed-on: http://gerrit.openafs.org/913