child-sa: Pass the number of total policies tied to an SA to the kernel

This will be useful if the kernel backend has to know how many policies
follow an SA install, for example if it must install all policies concurrently.

src/libcharon/sa/child_sa.c

@@ -847,6 +847,14 @@ METHOD(child_sa_t, add_policies, status_t,
 		priority = this->trap ? POLICY_PRIORITY_ROUTED
 							  : POLICY_PRIORITY_DEFAULT;
 
+		enumerator = create_policy_enumerator(this);
+		while (enumerator->enumerate(enumerator, &my_ts, &other_ts))
+		{
+			my_sa.policy_count++;
+			other_sa.policy_count++;
+		}
+		enumerator->destroy(enumerator);
+
 		/* enumerate pairs of traffic selectors */
 		enumerator = create_policy_enumerator(this);
 		while (enumerator->enumerate(enumerator, &my_ts, &other_ts))