LU-4971 ldlm: drop redundant ibits lock interoperability check

LU-4971 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is out of date for a long time.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>
Change-Id: I635df2767ed3b859d93b7ff0680e30ef07d94747
Reviewed-on: http://review.whamcloud.com/11004
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>