LU-17674 build: use nop_mnt_idmap in inode_owner_or_capable

LU-17674 build: use nop_mnt_idmap in inode_owner_or_capable

The build on kernel 6.7 reported the following errors:

     if (!inode_owner_or_capable(&init_user_ns, inode))
                                 ^~~~~~~~~~~~~
     note: expected 'struct mnt_idmap *' but argument is of
     type 'struct user_namespace *'

It replaces &init_user_ns with "nop_mnt_idmap" to fix the build
failure on new kernel.

Test-Parameters: trivial
Fixes: ce98bfe5f72 ("LU-10499 pcc: add readonly mode for PCC")
Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: I758ef5a074bb6449b2d703865010974d5135f241
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54572
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>