libmultipath: avoid frequent messages from filter_property()

Unlike the other filter functions, filter_property() is called
on every pathinfo() call, and prints a message with -v3 every
time. Avoid that by using a lower log priority for the call
from pathinfo().

Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>