staging: lustre: 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
version is equal to the current key_set_version.

In lu_context_refill, the key_set_version should be protected
before comparing it to version stored in the lu_context.

Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8346
Reviewed-on: https://review.whamcloud.com/26099
Reviewed-on: https://review.whamcloud.com/27448
Reviewed-on: https://review.whamcloud.com/27994


Reviewed-by: Patrick Farrell <paf@cray.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@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>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>