LU-1597 obdfilter: fix some capa code for OST

LU-1597 obdfilter: fix some capa code for OST

* A capability should be set for filter_sync(), and when the operation
  is come from OSS itself, the capability check can be passed.

* filter_capa_fixoa() need check whether filter enabled capability.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: Ie27497d2b61654a7f24c06f6975e8bfaf5e9ae13
Reviewed-on: http://review.whamcloud.com/3372
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Prakash Surya <surya1@llnl.gov>
Reviewed-by: Oleg Drokin <green@whamcloud.com>