Initialize Reader navigation with the saved feed

[crazytonyli]

This PR fix an issue in Reader:

1. Go to Reader -> Discover -> view a post. Note the post title.
2. Kill the app.
3. Search the post title on Spotlight, and tap the post result.
4. Jetpack app opens and shows the post. All looks good.
5. Tap the back button.

The app goes back, but also automatically pushes the Discover screen, which is unexpected.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	34418
	Version	PR #26003
	Bundle ID	com.jetpack.alpha
	Commit	1a0c22d
	Installation URL	4qvakm1k35a6o

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	34418
	Version	PR #26003
	Bundle ID	org.wordpress.alpha
	Commit	1a0c22d
	Installation URL	15ct2v8lomrn0

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.