staging/lustre/ldlm: drop redundant ibits lock interoperability check

In very old release (older than Lustre-1.8), if the client talks with
the server that does not support ibits lock, then the client needs to
convert it as plain lock. Such interoperability check and convertion
is out of date for a long time. Drop it.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Reviewed-on: http://review.whamcloud.com/11004
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4971


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>