dm mpath: fail message ioctl if specified path is not valid
Fail the reinstate_path and fail_path message ioctl if the specified
path is not valid.
The message ioctl would succeed for the 'reinistate_path' and
'fail_path' messages even if action was not taken because the
specified device was not a valid path of the multipath device.
Before, when /dev/vdb is not a path of mpathb:
$ dmsetup message mpathb 0 reinstate_path /dev/vdb
$ echo $?
0