Properly set the property_context for net.tcp_init_rwnd.

This property is many years old and it does not have a property
context associated with it. It is set by the system server (in
particular, ConnectivityService code, in the Tethering module)
and read by init, which does:

on property:net.tcp_def_init_rwnd=*
    write /proc/sys/net/ipv4/tcp_default_init_rwnd ${net.tcp_def_init_rwnd}

There is no need to add read access to init because init can read
and write any property.

Test: m
Fix: 170917042
Change-Id: I594b09656a094cd2ef3e4fd9703e46bf7b2edd4c
diff --git a/private/property.te b/private/property.te
index e4cbd7a..5d7dc2f 100644
--- a/private/property.te
+++ b/private/property.te
@@ -20,6 +20,7 @@
 system_internal_prop(localization_prop)
 system_internal_prop(lower_kptr_restrict_prop)
 system_internal_prop(net_464xlat_fromvendor_prop)
+system_internal_prop(net_connectivity_prop)
 system_internal_prop(netd_stable_secret_prop)
 system_internal_prop(pm_prop)
 system_internal_prop(rollback_test_prop)