LU-8346 obdclass: guarantee all keys filled

LU-8346 obdclass: guarantee all keys filled

In keys_fill, the key_set_version could be changed after
the keys are filled, then the keys in this context won't
be refilled by the following lu_context_refill for its
verion is equal to the current key_set_verion.

Change-Id: Ibaa49ec6e95ffee902cfa98f18ac9e66f2127bf1
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: https://review.whamcloud.com/26099
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>