fix(md): fix flicker when navigating back in MD mode on certain Android devices

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: #19491

What is the new behavior?

• The leaving view, when navigating back, has display: none applied to it at the end of the transition, ensuring that there is no flicker between when the animation is destroyed and when the view is removed from the DOM.

Does this introduce a breaking change?

• Yes
• No

Other information

[liamdebeasi]

Associated dev build: npm i @ionic/angular@4.11.0-dev.201910041827.7768ab2

[manucorporat]

I would like to know why this is a problem now, we haven't seen flickering before. I think it's important to understand why this is needed now, not against this change if we understand the root of the problem.