LU-11264 llapi: reduce llapi_stripe_limit_check() overhead

LU-11264 llapi: reduce llapi_stripe_limit_check() overhead

There is no need to check PAGE_SIZE in llapi_stripe_limit_check()
every time, since this cannot change between calls.

Always set errno if an error is returned.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ib377c1cc734c9e683f75eeb509e220c4ea3ebbe5
Reviewed-on: https://review.whamcloud.com/35091
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>