When a user clicks a navigation link in a dialog, close the dialog

Summary:
Ref T13302. Currently, if you enable Quicksand (by clicking "Persistent Chat"), open a dialog with links in it (like "Create Subtask" with multiple available subtypes), and then follow a navigation link, the page content reloads behind the dialog but the dialog stays in the foreground.

Fix this by closing dialogs when users click navigation links inside them.

Test Plan:
With Quicksand enabled and disabled, clicked a subtask type in the "Create Subtask" dialog.

• Before, Quicksand Disabled: Dialog stays on screen, then navigation occurs.
• After, Quicksand Disabled: Dialog vanishes, then navigation occurs.
• Before, Quicksand Enabled: Dialog stays on screen, navigation occurs behind it.
• After, Quicksand Enabled: Dialog vanishes, then navigation occurs.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13302

Differential Revision: https://secure.phabricator.com/D20573