LU-12093 osc: don't check capability for every page

LU-12093 osc: don't check capability for every page

We check CFS_CAP_SYS_RESOURCE for every page during the io.
This is expensive on apparmor enabled systems, we can only
do that once for the entire io and use the result when
submitting the pages.

Don't init the oap_brw_flags during osc_page_init(), the flag
will be set in either osc_queue_async_io() or osc_page_submit().

Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: I0e664f43ce31c276b33476fdff11794185ab0a3b
Reviewed-on: https://review.whamcloud.com/34478
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>