fix(mempool): Stop ignoring new transactions after the mempool is newly activated

[teor2345]

Motivation

Currently, when Zebra's mempool is newly activated, it skips adding newly verified transactions until the next request.

Instead, the first request to a newly activated mempool should show all available transactions.

This could be related to #6195, but I'm not sure if it is.

Specifications

Mempool transaction selection is a standard rule, so either implementation is valid here.

Solution

Only skip the reset when the mempool is newly activated, rather than skipping all of poll_ready().

Review

This is a routine mempool bug.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

[codecov]

Codecov Report

Merging #6448 (a2bbf09) into main (5db2243) will increase coverage by 0.04%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6448      +/-   ##
==========================================
+ Coverage   77.78%   77.83%   +0.04%     
==========================================
  Files         304      304              
  Lines       39637    39636       -1     
==========================================
+ Hits        30833    30852      +19     
+ Misses       8804     8784      -20     

[teor2345]

Temporary error:

ERROR: (gcloud.compute.instances.create-with-container) Could not fetch resource:

• Internal error. Please try again or contact Google Support. (Code: '5F864782189D7.6B5868C.50A111B')

https://github.com/ZcashFoundation/zebra/actions/runs/4591441080/jobs/8108460458?pr=6448#step:10:83

[arya2]

Looks good!