[ONOS] update command defect fix for cost type

Change-Id: I6cf35b6cd699904d15df7f08ca47d54e0b9c2138

@@ -47,7 +47,7 @@ public class PceUpdatePathCommand extends AbstractShellCommand {
 
     @Option(name = "-c", aliases = "--cost", description = "The cost attribute IGP cost (1) or TE cost (2).",
             required = false, multiValued = false)
-    int cost = 0;
+    int cost = -1;
 
     @Option(name = "-b", aliases = "--bandwidth", description = "The bandwidth attribute of path. "
             + "Data rate unit is in Bps.", required = false, multiValued = false)
@@ -66,12 +66,14 @@ public class PceUpdatePathCommand extends AbstractShellCommand {
         }
 
         // Cost validation
+        if (cost != -1) {
             if ((cost < 1) || (cost > 2)) {
                 error("The cost attribute value is either IGP cost(1) or TE cost(2).");
                 return;
             }
             CostConstraint.Type costType = CostConstraint.Type.values()[cost - 1];
             constrntList.add(CostConstraint.of(costType));
+        }
 
         if (!service.updatePath(TunnelId.valueOf(id), constrntList)) {
             error("Path updation failed.");