Exiting insert mode with escape doesn't close parameter hints

Issue Type: Bug

Describe the bug
After typing the first argument to a function and a comma used to denote the start of another argument, a popup of the function's signature is displayed above the cursor. It's expected that the popup will close after pressing the escape key, or exiting insert mode in my case. However, VSCode proceeds to exit insert mode without closing the popup, forcing me to click my mouse.

My current workaround is to disable parameter hints altogether with "editor.parameterHints.enabled": false in settings.json.

To Reproduce
Steps to reproduce the behavior:

1. Set language setting to Go
2. Ensure editor.parameterHints.enabled is set to true
3. Trigger parameter hints by invoking a function that takes more than one parameter but only provide the first argument followed by a comma
4. Press the escape key, which should also be key used to enter normal mode, and see that the popup displayed for the parameter hints feature doesn't close

Expected behavior
I expect my editor to both enter normal mode and close the popup after pressing escape.

I've disabled the vim plugin and verified that pressing escape in the specific case noted above will indeed close the popup.

Screenshots

Environment (please complete the following information):
Extension version: 1.7.0
VS Code version: Code 1.33.1 (51b0b28134d51361cf996d2f0a1c698247aeabd8, 2019-04-11T08:22:55.268Z)
OS version: Darwin x64 18.5.0

Reproduce the issue in VS Code with the Vim extension enabled, Go selected, and editor.parameterHints.enabled set to true, then trigger parameter hints and press Escape. Trace the extension's insert-mode Escape handling and parameter-hint interaction; done means Escape both enters normal mode and closes the parameter-hint popup.