(GH-516) Fix: Log.InitializeWith doesn't clear cached loggers

This mostly affects the specs - if you use the loggers and then later
initialize them with a logger, the already initialized loggers will
still use the NullLogger because they were not cleared.

This could also lead to some very interesting behavior when using the
dll version of Chocolatey.

src/chocolatey/LogExtensions.cs

@@ -42,6 +42,14 @@ public static class LogExtensions
         //     return Log(objectName);
         //}
 
+        /// <summary>
+        /// Resets the loggers. This allows switching to a new logger and not reusing old loggers that may be already cached.
+        /// </summary>
+        public static void ResetLoggers()
+        {
+            _dictionary.Value.Clear();
+        }
+
         /// <summary>
         ///   Gets the logger for <see cref="T" />.
         /// </summary>

src/chocolatey/infrastructure/logging/Log.cs

@@ -34,6 +34,7 @@ public static class Log
         public static void InitializeWith<T>() where T : ILog, new()
         {
             _logType = typeof (T);
+            LogExtensions.ResetLoggers();
         }
 
         /// <summary>
@@ -45,6 +46,7 @@ public static void InitializeWith(ILog loggerType)
         {
             _logType = loggerType.GetType();
             _logger = loggerType;
+            LogExtensions.ResetLoggers();
         }
 
         /// <summary>