LU-14739 quota: fix quota with root squash enabled

LU-14739 quota: fix quota with root squash enabled

This patch tries to fix several problems:

1. OSD will ignore quota if IO comes from client
cache or root, however since following change:

LU-12687 osc: consume grants for direct I/O

DIO now consumes grant too, following check for
sync IO is wrong now:

(lnb[i].lnb_flags & (OBD_BRW_FROM_GRANT | OBD_BRW_SYNC))
        == OBD_BRW_FROM_GRANT)

This wass originally added to support 1.8 client, it is
going to be 2.15 now, so let's remove this broken check.

2. Server side will clear OBD_BRW_NOQUOTA if root squash
is enabled, this will revert fixes from:

"LU-13228 clio: mmap write when overquota"

We need to separate @ci_noquota and @oi_cap_sys_resource cases,
introduce a new flag OBD_BRW_SYS_RESOURCE, and extend test_75
to cover this case.

3. LU-14739 missed case that DoM quota should be considered
as well.

4. If EDQUOT is returned for root, we check the new root squash
flag OBD_FL_ROOT_SQUASH from server side. If this flag is not set,
we bypass quota for root, otherwise all root writes become sync
writes.

5. Fix a leftover problem with LU-9671 for DOM

Fixes: a4fbe7341baf12 ("LU-14739 quota: nodemap squashed root cannot bypass quota")
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Signed-off-by: Wang Shilong <wangshilong1991@gmail.com>
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I3fd23da7d56acb5b485540333208e5d5b0b48023
Reviewed-on: https://review.whamcloud.com/44347
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>