selinux: get netif_wildcard policycap from policy instead of cache

Retrieve the netif_wildcard policy capability in security_netif_sid()
from the locked active policy instead of the cached value in
selinux_state.

Fixes: 8af43b61 ("selinux: support wildcard network interface names")
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[PM: /netlabel/netif/ due to a typo in the description]
Signed-off-by: Paul Moore <paul@paul-moore.com>