Reading ports from environment if specified

Change-Id: I14377922d081705a5aede5aeabb2f3c9befda06f
diff --git a/voltha b/voltha
index 2a2af90..34e4c84 100755
--- a/voltha
+++ b/voltha
@@ -663,18 +663,18 @@
 
    # create new ports starting from the first available
    DELTA="$((START - 81))"
-   ONOS_API_PORT=${START}81
-   ONOS_SSH_PORT=${START}01
-   VOLTHA_API_PORT=5$((55 + DELTA))55
-   VOLTHA_SSH_PORT=$((50 + DELTA))22
-   VOLTHA_ETCD_PORT=$((23 + DELTA))79
-   VOLTHA_KAFKA_PORT=$((90 + DELTA))92
-   VOLTHA_PPROF_PORT=$((60 + DELTA))60
-   OPENOLT_PPROF_PORT=$((60 + DELTA))61
-   OFAGENT_PPROF_PORT=$((60 + DELTA))62
-   ELASTICSEARCH_PORT=$((92 + DELTA))00
-   KIBANA_PORT=$((56 + DELTA))01
-   TRACING_GUI_PORT=$((66 + DELTA))86
+    ONOS_API_PORT=${ONOS_API_PORT:-${START}81}
+    ONOS_SSH_PORT=${ONOS_SSH_PORT:-${START}01}
+    VOLTHA_API_PORT=${VOLTHA_API_PORT:-5$((55 + DELTA))55}
+    VOLTHA_SSH_PORT=${VOLTHA_SSH_PORT:-$((50 + DELTA))22}
+    VOLTHA_ETCD_PORT=${VOLTHA_ETCD_PORT:-$((23 + DELTA))79}
+    VOLTHA_KAFKA_PORT=${VOLTHA_KAFKA_PORT:-$((90 + DELTA))92}
+    VOLTHA_PPROF_PORT=${VOLTHA_PPROF_PORT:-$((60 + DELTA))60}
+    OPENOLT_PPROF_PORT=${OPENOLT_PPROF_PORT:-$((60 + DELTA))61}
+    OFAGENT_PPROF_PORT=${OFAGENT_PPROF_PORT:-$((60 + DELTA))62}
+    ELASTICSEARCH_PORT=${ELASTICSEARCH_PORT:-$((92 + DELTA))00}
+    KIBANA_PORT=${KIBANA_PORT:-$((56 + DELTA))01}
+    TRACING_GUI_PORT=${TRACING_GUI_PORT:-1$((66 + DELTA))86}
 fi
 
 PORTTMP="$(mktemp -u)"