LU-7802 ldlm: No -EINVAL for canceled != unused

LU-7802 ldlm: No -EINVAL for canceled != unused

If any locks are removed from or added to the lru, the
check of "number unused vs number cancelled" may be wrong.
This is fine - do not return an error or print debug in
this case.

Signed-off-by: Patrick Farrell <paf@cray.com>
Change-Id: I2ee9b8d86fbd6c9bd2c29e3472e3d410ee303374
Reviewed-on: https://review.whamcloud.com/28560
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>