ueventd: allow getattr on blk and chr types.

The commit: d41ad551
fixes a race in coldboot. However, introduced a seperate
bug where existing character files were being relabeled.

The fix was to have ueventd ensure their was a delta between
the old and new labels and only then call lsetfilecon(). To
do this we call lgetfilecon() which calls lgetxattr(), this
requires getattr permissions.

This patch is void of any relabelfrom/to for ueventd on chr_file
as those can be added as they occur.

Bug: 29106809

Change-Id: I84f60539252fc2b4a71cf01f78e3cadcfad443ef
Signed-off-by: William Roberts <william.c.roberts@intel.com>