RATIS-2043. Change toString() of RaftConfigurationImpl (#1051)

diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java
index d609264..98f4102 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java
@@ -298,7 +298,7 @@
 
   @Override
   public String toString() {
-    return logEntryIndex + ": " + conf + ", old=" + oldConf;
+    return "conf: {index: " + logEntryIndex + ", cur=" + conf + ", old=" + oldConf + "}";
   }
 
   boolean hasNoChange(Collection<RaftPeer> newMembers, Collection<RaftPeer> newListeners) {
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
index e8aeb66..23cab70 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
@@ -1210,7 +1210,7 @@
 
       if (!conf.isHighestPriority(request.getNewLeader())) {
         String msg = getMemberId() + " refused to transfer leadership to peer " + request.getNewLeader() +
-            " as it does not has highest priority " + conf;
+            " as it does not has highest priority in " + conf;
         return logAndReturnTransferLeadershipFail(request, msg);
       }