Tests: add one for .DatabaseCount

StackExchange.Redis.Tests/Databases.cs

@@ -41,6 +41,20 @@ public async Task CountKeys()
             }
         }
 
+        [Fact]
+        public void DatabaseCount()
+        {
+            using (var muxer = Create(allowAdmin: true))
+            {
+                var server = GetAnyMaster(muxer);
+                var count = server.DatabaseCount;
+                Log("Count: " + count);
+                var configVal = server.ConfigGet("databases")[0].Value;
+                Log("Config databases: " + configVal);
+                Assert.Equal(int.Parse(configVal), count);
+            }
+        }
+
         [Fact]
         public void MultiDatabases()
         {