=rem #19228 make the default TLS version 1.2

TLS 1.2 should be preferred and we always have it available by virtue of requiring JDK8 for Akka 2.4.x.
See also https://blogs.oracle.com/java-platform-group/entry/java_8_will_use_tls

akka-remote/src/test/scala/akka/remote/Ticket1978CommunicationSpec.scala

@@ -47,7 +47,7 @@ object Configuration {
           key-store-password = "changeme"
           key-password = "changeme"
           trust-store-password = "changeme"
-          protocol = "TLSv1"
+          protocol = "TLSv1.2"
           random-number-generator = "%s"
           enabled-algorithms = [%s]
         }