Nat-related commands refine

We need this to ensure that the tethering IPCs don't need to grab the
lock in two different controllers

The idea is that always having a global_alert rule in bw_global_alert
chain.
TetherController will enable/disable the reference of bw_global_alert
chain.

[childchain order of filter FORWARD chain]
Chain FORWARD
   nm_mdmprxy_iface_pkt_fwder
   oem_fwd
   fw_FORWARD
   bw_FORWARD
   tetherctrl_FORWARD

--Simple rule comparison--
[Before]
Chain bw_FORWARD
    Alert rule
    ... other rules
Chain tetherctrl_FORWARD
    ... other rules
[After]
Chain bw_FORWARD
    No Alert rule
    ... other rules
Chain tetherctrl_FORWARD
    Jump to bw_global_alert
    ... other rules
Chain bw_global_alert
   Alert rule

The exact rule comparison is shown in the bug.

Bug:119735985
Test: built, flashed, booted
      system/netd/tests/runtests.sh passes

Change-Id: Ibf752d0c8de9170689fc74c89c0424d2642853ec
diff --git a/server/BandwidthController.h b/server/BandwidthController.h
index 31575b8..b8691dc 100644
--- a/server/BandwidthController.h
+++ b/server/BandwidthController.h
@@ -73,6 +73,7 @@
     static const char LOCAL_OUTPUT[];
     static const char LOCAL_RAW_PREROUTING[];
     static const char LOCAL_MANGLE_POSTROUTING[];
+    static const char LOCAL_GLOBAL_ALERT[];
 
     enum IptJumpOp { IptJumpReject, IptJumpReturn, IptJumpNoAdd };
     enum IptOp { IptOpInsert, IptOpDelete };
@@ -136,15 +137,6 @@
     int64_t mSharedQuotaBytes = 0;
     int64_t mSharedAlertBytes = 0;
     int64_t mGlobalAlertBytes = 0;
-    /*
-     * This tracks the number of tethers setup.
-     * The FORWARD chain is updated in the following cases:
-     *  - The 1st time a globalAlert is setup and there are tethers setup.
-     *  - Anytime a globalAlert is removed and there are tethers setup.
-     *  - The 1st tether is setup and there is a globalAlert active.
-     *  - The last tether is removed and there is a globalAlert active.
-     */
-    int mGlobalAlertTetherCount = 0;
 
     std::map<std::string, QuotaInfo> mQuotaIfaces;
     std::set<std::string> mSharedQuotaIfaces;