proc/get_seclabel: catch the error when no security module is active
proc/get_seclabel: catch the error when no security module is active

In this case, reading from the attr file will return -EINVAL, which
we will handle gracefully by treating it as the empty label (in the
same way as we do for the sockopt).

Signed-off-by: Tom Gundersen <7c8224529a7c718e876cb2496c973509fde1e50e@jklm.no>

bus1/dbus-broker