util/util-security: scala2.13 compat for MapValues

Problem

scala2.13 introduce a breaking change to mapValues to return a view instead of a map. This broke the util-security build which was updated in D617641 to use mapValues.

Solution

Force the view into a map with `toMap`

Result

util-security can build for scala2.13

JIRA Issues: PSEC-10357

Differential Revision: https://phabricator.twitter.biz/D787935

Author: jcrawford13

util-security/src/main/scala/com/twitter/util/security/Credentials.scala

@@ -44,7 +44,7 @@ object Credentials {
   def apply(data: String): Map[String, String] = {
     val result: java.util.Map[String, Any] = parser.get.load(data)
     Option(result)
-      .map(_.asScala.toMap.mapValues(v => if (v == null) "null" else v.toString)).getOrElse(
+      .map(_.asScala.toMap.mapValues(v => if (v == null) "null" else v.toString).toMap).getOrElse(
         Map.empty)
   }
 }