Fix trailing backslash in path of GetFileInformation()/OpenDirectory() call during SetAccessControl()

[viciousviper]

When calling SetAccessControl() on a DirectoryInfo instance in C# the call sequence executed on a mounted IDokanOperationsProxy contains several calls with a redundant trailing backslash character:

OpenDirectory ("\Dir***", ...)
GetFileInformation ("\Dir***",...)
Cleanup ("\Dir***", ...)
CloseFile ("\Dir***", ...)

This is the only known case where dokany calls the IDokanOperationsProxy with a trailing backslash in the filename (actually a directory name). Even in the same call sequence all other methods use the directory name without the trailing slash.
Please change the call pattern so that all file/directory paths are consistently named without a trailing backslash - with the exception of the root directory path \.

See below for the full call sequence taken from a trace of the test DirectoryInfoTest.SetAccessControl_CallsApiCorrectly() in the DokanNet.Tests project.
Relevant filenames are emphasized in bold.

CreateFile[1] ("", ..)
GetFileInformation[1] ("", ...)
Cleanup[1] ("", ...)
CloseFile[0] ("", ...)
CreateFile[1] ("\Dir", ...)
GetFileInformation[1] ("\Dir", ...)
CreateFile[2] ("", ...)
GetFileInformation[2] ("", ...)
GetFileSecurity[2] ("", ...)
Cleanup[2] ("", ...)
CloseFile[1] ("", ...)
GetFileInformation[1] ("\Dir", ...)
GetFileSecurity[1] ("\Dir", ...)
OpenDirectory[2] ("\Dir", ...)
GetFileInformation[2] ("\Dir", ...)
Cleanup[2] ("\Dir", ...)
CloseFile[1] ("\Dir", ...)
OpenDirectory[2] ("\Dir", ...)
GetFileInformation[2] ("\Dir", ...)
Cleanup[2] ("\Dir", ...)
CloseFile[1] ("\Dir", ...)
SetFileSecurity[1] ("\Dir", ..)
OpenDirectory[2] ("\Dir", ..)
GetFileInformation[2] ("\Dir", ..)
Cleanup[2] ("\Dir", ...)
CloseFile[1] ("\Dir", ...)
OpenDirectory[2] ("\Dir", ...)
GetFileInformation[2] ("\Dir", ...)
Cleanup[2] ("\Dir", ...)
CloseFile[1] ("\Dir", ...)
Cleanup[1] ("\Dir", ...)
Waiting for closure (#1)
CloseFile[0] ("\Dir", ...)

[Liryna]

This should make the work.
(I was not able to reproduce the "\Dir" to test).

[Maxhy]

@Liryna The changes are wrong.
Among other things it breaks directory rename when the directory is located at root drive.

[Maxhy]

Reverted the 'empty filename change' only which was a wrong fix and cause the new bug, with commit 4496617.