LU-9145 nodemap: new_init_ucred doesn't do nodemapping

LU-9145 nodemap: new_init_ucred doesn't do nodemapping

The new_init_ucred path was missed in the original nodemap
implementation. This patch adds the mapping calls to new_init_ucred.

WIP: There are some issues/questions:
 - some of the new_init_ucred code should be merged with
	old_init_ucred_common.
 - Why does new_init check for setuid/setgid/setgrp, but not old_init?
 - What is ptlrpc_user_desc and should it interact with nodemap?

Lustre-change: https://review.whamcloud.com/26624
Lustre-commit: 37db778f48f952747575e323cb341ed663852fff

Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: Ia0e07078f32c43ec319be5a4cea753667056d645
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/30812
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>