Add an internal config table to apply unexposed configurations to swi…

…tch before testing (#638)

This PR renamed the table `underlay_mac` to `internal_config`. The new
`internal_config` table is ignored for SAI API generation and will be
used for setting switch to an initial state required by some test cases.

dash-pipeline/bmv2/dash_pipeline.p4

@@ -234,7 +234,6 @@ control dash_ingress(
     }
 
     apply {
-        meta.flow_enabled = false;
 
 #ifndef TARGET_DPDK_PNA
         meta.rx_encap.setValid();

dash-pipeline/bmv2/stages/pre_pipeline.p4

@@ -25,21 +25,23 @@ control pre_pipeline_stage(inout headers_t hdr,
         const default_action = accept;
     }
 
-    action set_underlay_mac(EthernetAddress neighbor_mac,
-                            EthernetAddress mac) {
+    action set_internal_config(EthernetAddress neighbor_mac,
+                            EthernetAddress mac,
+                            bit<1> flow_enabled) {
         meta.u0_encap_data.underlay_dmac = neighbor_mac;
         meta.u0_encap_data.underlay_smac = mac;
+        meta.flow_enabled = (bool)flow_enabled;
     }
 
-    /* This table API should be implemented manually using underlay SAI */
+    /* This table API should be implemented manually using SAI */
     @SaiTable[ignored = "true"]
-    table underlay_mac {
+    table internal_config {
         key = {
             meta.appliance_id : ternary;
         }
 
         actions = {
-            set_underlay_mac;
+            set_internal_config;
         }
     }
 
@@ -120,7 +122,7 @@ control pre_pipeline_stage(inout headers_t hdr,
         }
 
         appliance.apply();
-        underlay_mac.apply();
+        internal_config.apply();
     }
 }