Fixed: Avoid import loop for already imported albums

(cherry picked from commit b183743d9f0a0b15e4a9db0a9d3d2d1c238b0d9c)

Closes #4231

src/NzbDrone.Core.Test/MediaFiles/TrackImport/Specifications/AlreadyImportedSpecificationFixture.cs

@@ -141,7 +141,7 @@ namespace NzbDrone.Core.Test.MediaFiles.TrackImport.Specifications
 
             GivenHistory(history);
 
-            Subject.IsSatisfiedBy(_localAlbumRelease, _downloadClientItem).Accepted.Should().BeTrue();
+            Subject.IsSatisfiedBy(_localAlbumRelease, _downloadClientItem).Accepted.Should().BeFalse();
         }
     }
 }

src/NzbDrone.Core/MediaFiles/TrackImport/Specifications/AlreadyImportedSpecification.cs

@@ -67,6 +67,11 @@ namespace NzbDrone.Core.MediaFiles.TrackImport.Specifications
                     return Decision.Reject("Album already imported at {0}", lastImported.Date.ToLocalTime());
                 }
             }
+            else
+            {
+                _logger.Debug("Album previously imported at {0}", lastImported.Date);
+                return Decision.Reject("Album already imported at {0}", lastImported.Date.ToLocalTime());
+            }
 
             return Decision.Accept();
         }