Fixed curl multithreaded access.

src/NzbDrone.Common/Http/CurlHttpClient.cs

@@ -39,6 +39,8 @@ namespace NzbDrone.Common.Http
         }
 
         public HttpResponse GetResponse(HttpRequest httpRequest, HttpWebRequest webRequest)
+        {
+            lock (CurlGlobalHandle.Instance)
             {
                 Stream responseStream = new MemoryStream();
                 Stream headerStream = new MemoryStream();
@@ -91,6 +93,7 @@ namespace NzbDrone.Common.Http
 
                 return new HttpResponse(httpRequest, httpHeader, responseData, (HttpStatusCode)curlEasy.ResponseCode);
             }
+        }
 
         private CurlSlist SerializeHeaders(HttpWebRequest webRequest)
         {
@@ -205,6 +208,8 @@ namespace NzbDrone.Common.Http
         }
 
         public bool Initialize()
+        {
+            lock (CurlGlobalHandle.Instance)
             {
                 if (_initialized)
                     return _available;
@@ -214,6 +219,7 @@ namespace NzbDrone.Common.Http
 
                 return _available;
             }
+        }
 
         protected override bool ReleaseHandle()
         {