clean xml tags of invalid characters. Fixes #3305

lib/devices/android/bootstrap/src/io/appium/android/bootstrap/utils/XMLHierarchy.java

@@ -145,6 +145,10 @@ public abstract class XMLHierarchy {
     }
   }
 
+  // set the node's tag name to the same as it's android class.
+  // also number all instances of each class with an "instance" number. It increments for each class separately.
+  // this allows use to use class and instance to identify a node.
+  // we also take this chance to clean class names that might have dollar signs in them (and other odd characters)
   private static void visitNode(Node node, HashMap<String, Integer> instances) {
 
     Document doc = node.getOwnerDocument();
@@ -157,6 +161,8 @@ public abstract class XMLHierarchy {
       return;
     }
 
+    androidClass = cleanTagName(androidClass);
+
     if (!instances.containsKey(androidClass)) {
       instances.put(androidClass, 0);
     }
@@ -170,4 +176,9 @@ public abstract class XMLHierarchy {
 
     instances.put(androidClass, instance+1);
   }
+
+  private static String cleanTagName(String name) {
+    name = name.replaceAll("[$@#&]", ".");
+    return name.replaceAll("\\s", "");
+  }
 }