bug: App can only find robots if "Try again" is clicked after the interface comes up

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Overview

Clicking the "Try again" / "Refresh list" button doesn't do anything useful if the network interface wasn't already up when you clicked the button.

It takes ~20–25 seconds for the link-local network interface to come up after plugging in an OT-2, so if you plug in an OT-2 and immediately click the button, the 30 second discovery period will be wasted. This is one reason why people might have to click "Try again" more than once to see the robot that they just plugged in.

Current behavior

Quoth the @mcous:

...the mDNS browser only checks the computer's interface list for binding at the beginning of any given discovery period, and won't refresh that list until a new fast discovery period is started (for example, by clicking the button).

Expected behavior

• If an interface comes up in the middle of a "Try again" / "Refresh list" fast discovery period, discovery requests should go out on that interface, just like the interfaces that were up before the discovery period started.
• If an interface comes up during slow discovery (when I haven't clicked the button and the app is just sitting idle), discovery requests should automatically start going out on that interface.

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Workaround

(Simple, but documenting this here for posterity.)

1. Turn on and plug in your OT-2.
2. Wait 2 minutes.
3. Then click Try again or Refresh list.