netlabel: fix our progress tracking in netlbl_unlabel_staticlist()

The current NetLabel code doesn't correctly keep track of the netlink
dump state in some cases, in particular when multiple interfaces with
large configurations are loaded.  The problem manifests itself by not
reporting the full configuration to userspace, even though it is
loaded and active in the kernel.  This patch fixes this by ensuring
that the dump state is properly reset when necessary inside the
netlbl_unlabel_staticlist() function.

Fixes: 8cc44579

 ("NetLabel: Introduce static network labels for unlabeled connections")
Signed-off-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/160484450633.3752.16512718263560813473.stgit@sifl
Signed-off-by: Jakub Kicinski <kuba@kernel.org>