staging: lustre: libcfs: invert test condition for libcfs_ioctl

staging: lustre: libcfs: invert test condition for libcfs_ioctl

Invert the test of error returned by the handle_ioctl pointer.
This reduces the code by one indentation level.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5435
Reviewed-on: http://review.whamcloud.com/11313
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>