Fix flicker on mouse over in download button.

[ntoll]

Description

Fixes #791

A trivial change. Took a while to spot why the flicker was happening. Parenthesis to clarify logical order of precedence.

Test Plan

No unit test change needed. Eyeball Mk.1 used to confirm flickering no longer happens. 👀

Checklist

If these changes modify code paths involving cryptography, the opening of files in VMs or network (via the RPC service) traffic, Qubes testing in the staging environment is required. For fine tuning of the graphical user interface, testing in any environment in Qubes is required. Please check as applicable:

• I have tested these changes in the appropriate Qubes environment
• I do not have an appropriate Qubes OS workstation set up (the reviewer will need to test these changes)
• These changes should not need testing in Qubes

If these changes add or remove files other than client code, packaging logic (e.g., the AppArmor profile) may need to be updated. Please check as applicable:

• I have submitted a separate PR to the packaging repo
• No update to the packaging logic (e.g., AppArmor profile) is required for these changes
• I don't know and would appreciate guidance

[sssoleileraaa]

I'm unable to repro #791 in Qubes (R4.0) so i can't confirm this fixes it. Perhaps someone else can? Also, it would be helpful if system information could be documented somewhere in case this happens again.

[ntoll]

@creviera I was able to reproduce this on my Ubuntu 18.04 development laptop.

[eloquence]

I'm also still able to repro #791 in Qubes (easiest by DL'ing a large file, and then repeatedly mousing over the spinner).

I can also confirm that this PR fixes the issue for me (tested with 25aeb2c cherry-picked to unbreak client in Qubes). 🎉

[eloquence]

However, the download icon behavior is not what I'm expecting (decoupled hover states again), testing whether this is a regression introduced by this PR or not.

Edit: Nope, that's #804, and is unrelated to this PR.

[ntoll]

Rebased and clarified the comment about random (but regular) crashes of the test suite.

[sssoleileraaa]

Just to make it clear the requested changes are just this: #792 (review) (the removal of HoverMOve and the comment or a comment replacement with an issue link so we can work on repro'ing and track)

[ntoll]

@creviera @eloquence all ready for review after Friday's force push. Apologies for not flagging this.

[sssoleileraaa]

lgtm