VOL-1296 - OpenOLT driver doesn't enable NNIs on some platforms

Changed OpenOLT agent to enable NNIs at same time it enables PONs during
initial terminal connection to BAL. Made it intelligent to check
current config to avoid errors in BAL that are thrown if already
enabled.

Change-Id: I7914900f2f64654d223961108c3b78bc856b66ef
diff --git a/src/indications.cc b/src/indications.cc
index b0ba964..fd40603 100644
--- a/src/indications.cc
+++ b/src/indications.cc
@@ -87,6 +87,15 @@
         }
     }
 
+    // Enable all NNI interfaces. 
+    // 
+    for (int i = 0; i < NumNniIf_(); i++) {
+        status = EnableUplinkIf_(i);
+        if (!status.ok()) {
+            // FIXME - raise alarm to report error in enabling PON
+        }
+    }
+
     /* register for omci indication */
     {
         bcmbal_cb_cfg cb_cfg = {};