fix: don't make keypool refill spam progress bars

[panleone]

Issue being fixed or feature implemented

Trivial bug: keypoolrefill internally updates the status of the progress bar each second.

m_storage.UpdateProgress(strMsg, static_cast<int>(dProgress));

However it can happen that one second is not enough time to make significant progress and
static_cast<int>(dProgress) = 0.
Calling the function with 0 as progress opens a new progress bar and this led to problems like #5730

What was done?

trivially make sure to update the progress only if the parameter is >0

How Has This Been Tested?

rpc does not spam anymore

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

[kxcd]

This bug impacted me when generating a large quantity of keys, eg 1,000,000.

[UdjinM6]

Nice find! 👍 ACK

[PastaPastaPasta]

utACK for squash merge