Undo via `u` does not remove file dirty flag

Describe the bug Using u to undo changes doesn’t restore the file to a clean state when reverting back to the original file that was opened.

To Reproduce Steps to reproduce the behaviour:

1. open file
2. enter insert mode
3. insert a space, observe tab has dirty icon
4. exit to normal mode and press u to remove change
5. File is still considered dirty

Expected behaviour If you perform this same operation but instead of pressing u you press ctrl+z the file will return to a clean state, this should be the same for u

Environment (please complete the following information):

• Extension (VsCodeVim) version: 0.16.12
• VSCode version: 1.28.2
• OS: Ubuntu 18 LTS

Additional context Related issue in vscode for context https://github.com/Microsoft/vscode/issues/919

[abbondanza]

Here’s a quick solution to this problem (until there’s an official one):

    "vim.normalModeKeyBindings": [
        {
            "before" : ["u"],
            "commands" : [
                "undo"
            ]
        },
        {
            "before" : ["<C-r>"],
            "commands" : [
                "redo"
            ]
        }
    ]

[MrHate]

Here’s a quick solution to this problem (until there’s an official one):

    "vim.normalModeKeyBindings": [
        {
            "before" : ["u"],
            "commands" : [
                "undo"
            ]
        },
        {
            "before" : ["<C-r>"],
            "commands" : [
                "redo"
            ]
        }
    ]

A confusing point is, after I use O to produce an indented new line, I need to press u twice to undo this operation. One for the indent, the other one for the new line.