Move pf_key socket creation permission to system_server

Allow system_server to trigger the kernel synchronize rcu with open and
close pf_key socket. This action was previously done by netd but now
it need to be done by system_server instead because the handling code in
netd are moved to mainline module which will be loaded by system_server
in JNI mode.

Note: the permission will be removed from netd once all bpf interactions
have moved out of netd.

Bug: 202086915
Test: android.app.usage.cts.NetworkUsageStatsTest
      android.net.cts.TrafficStatsTest
Change-Id: I440e0c87193775115a9b9ffb19270c47b01b082e
diff --git a/private/netd.te b/private/netd.te
index d87b9a6..a0c8f8f 100644
--- a/private/netd.te
+++ b/private/netd.te
@@ -18,6 +18,7 @@
 
 # in order to invoke side effect of close() on such a socket calling synchronize_rcu()
 # TODO: Remove this permission when 4.9 kernel is deprecated.
+# TODO: Remove this after we remove all bpf interactions from netd.
 allow netd self:key_socket create;
 
 set_prop(netd, ctl_mdnsd_prop)