Hide indicator popover when entering gala overview/multitasking view

## Prerequisites
- [x] I have searched open and closed issues for duplicates.

## Describe the bug
For example, you open applications-menu and go into overview or multitasking view the popover will be visible in the overview (not pretty), or in multitasking view wingpanel slides back in with the indicator open.

The latter isn't as ugly because the desktop is obscured and there's an animation, but I feel if you've unfocused these elements they should become hidden/closed.

### To Reproduce
Steps to reproduce the behavior:
1. Open an indicator in wingpanel.
2. Open windows overview or multitasking view (gala).
3. Notice the indicator is visible in the overview, or in multitasking view wingpanel slides back into view with the indicator open.

### Expected behavior
The indicator will become hidden as it's no longer the focus, you've navigated to some sort of window management.