Accept the same boolean values in RestRequest

Added `no` as a possible value to `paramBooleanAsOptional`, also reused existing code from `Booleans.parseBoolean`

Closes #4808

Author: javanna

src/main/java/org/elasticsearch/rest/RestRequest.java

@@ -136,11 +136,7 @@ public boolean paramAsBoolean(String key, boolean defaultValue) {
 
     @Override
     public Boolean paramAsBooleanOptional(String key, Boolean defaultValue) {
-        String sValue = param(key);
-        if (sValue == null) {
-            return defaultValue;
-        }
-        return !(sValue.equals("false") || sValue.equals("0") || sValue.equals("off"));
+        return Booleans.parseBoolean(param(key), defaultValue);
     }
 
     public TimeValue paramAsTime(String key, TimeValue defaultValue) {