add trim for descriptionPropertyValue (jenkinsci#100)

try to fix jenkinsci#81

for selectContent.jelly  <j:forEach var="value" items="${effectiveValue}"> this will be trim by jelly tag forEach.

for computeDefaultValue this will be trim by method computeDefaultValueMap

but descriptionPropertyValue was not trim.

Change-Id: Ic05be1679436d7c6c80c4d585a301acfbeaa5cc7

src/main/java/com/cwctravel/hudson/plugins/extended_choice_parameter/ExtendedChoiceParameterDefinition.java

@@ -376,7 +376,7 @@ private Map<String, String> computeDescriptionMap(String effectiveValue) {
                 descMap = new HashMap<>();
                 String[] descA = Iterables.toArray(Splitter.on(multiSelectDelimiter).split(desc), String.class);
                 for (int i = 0; i < values.length && i < descA.length; i++) {
-                    descMap.put(values[i], descA[i]); // 每个value和每个description一一对应.
+                    descMap.put(StringUtils.trim(values[i]), StringUtils.trim(descA[i])); // 每个value和每个description一一对应.
                 }
             }
         }