staging: lustre: llite: remove IS_ERR(master_inode) check

The kernel function ilookup5_nowait never returns
IS_ERR so we can remove the IS_ERR check in the
ll_md_blocking_ast() function.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8697
Reviewed-on: http://review.whamcloud.com/23151


Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Frank Zago <fzago@cray.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>