LU-221 don't use a/c/m time for newly allocated object in OST

LU-221 don't use a/c/m time for newly allocated object in OST

in OST, the a/c/m time is unusable for newly allocated object for
it has not gotten valid time info from clients. by setting the a/c/m
time as LONG_MIN at creation will make the clients ignore the time.

Change-Id: I0d6094e4257626ffd1128b3540837deaf230e056
Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1084
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>