Fix projid accounting for xattr objects

zpool upgraded with 'feature@project_quota' needs re-layout of SA's
to fix the SA_ZPL_PROJID at SA_PROJID_OFFSET (128). Its necessary for
the correct accounting of object usage against its projid.
Old object (created before upgrade) when gets a projid assigned, its
SA gets re-layout via sa_add_projid(). If object has xattr dir, SA
of xattr dir also gets re-layout. But SA re-layout of xattr objects
inside a xattr dir is not done.

Fix zfs_setattr_dir() to re-layout SA's on xattr objects, when setting
projid on old xattr object (created before upgrade).

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Jitendra Patidar <jitendra.patidar@nutanix.com>
Closes #16355
Closes #16356