LU-10244 osc: add a bit to indicate osc_page in cache tree

LU-10244 osc: add a bit to indicate osc_page in cache tree

Add osc_page::ops_intree to indicate whether the osc_page is in the
osc_object's cache tree, so that when page cannot insert in the
cache as race happens, the cleanup code won't try to remove it from
the cache.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Ifcfe158d10c23a40c116414c7f4f86b257e1fa76
Reviewed-on: https://review.whamcloud.com/30096
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>