LU-8697 llite: remove IS_ERR(master_inode) check

LU-8697 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.

Change-Id: I5e72a8f70857f178a2377e9db80b2e2139c56ec3
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/23151
Tested-by: Jenkins
Reviewed-by: Frank Zago <fzago@cray.com>
Tested-by: Maloo <hpdd-maloo@intel.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>