Discard the stale workingcopies that belonged to the deleted folder

[testforstephen]

Signed-off-by: Jinbo Wang jinbwan@microsoft.com

[testforstephen]

When renaming a package A to B, the received file events are like [ B: created, parent: changed, A: Deleted]. If there are sub files under package A being opened before, the working copies they produced are probably not released. One bad thing about these stale workingcopies is that they may produce some garbage diagnostics, because the publish diagnostics job in the DocumentLifeCycleHandler will iterate all workingcopies and report their diagnostics to client.

[fbricon]

@testforstephen thanks!