Add InterfaceConfiguration.isUp()

Bug: 31337216
Test: None
Change-Id: Ifd83b069472fc50c9517fc69306e7938a9e9628c

core/java/android/net/InterfaceConfiguration.java

@@ -124,6 +124,10 @@ public class InterfaceConfiguration implements Parcelable {
         return false;
     }
 
+    public boolean isUp() {
+        return hasFlag(FLAG_UP);
+    }
+
     /** {@inheritDoc} */
     public int describeContents() {
         return 0;