capabitlies: ns_capable can use the cap helpers rather than lsm call

Just to reduce the number of places to change if we every change the LSM
hook, use the capability helpers internally when possible.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>
diff --git a/kernel/capability.c b/kernel/capability.c
index 5f99e5d..4762644 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -384,7 +384,7 @@
 		BUG();
 	}
 
-	if (security_capable(current_cred(), ns, cap) == 0) {
+	if (has_ns_capability(current, ns, cap)) {
 		current->flags |= PF_SUPERPRIV;
 		return true;
 	}