Ensure server is started before handling requests

[fasmat]

Motivation

Fixes #6113. Ensures that when the p2p servier is started requests aren't handled before protocols are available.

Description

Before doing anything in the p2p.Server.Run method ensure that the muxer has at least one protocol available.

Test Plan

• without this fix Test_GetAtxsLimiting fails in about 2% of all test runs on my machine. With this change 500 runs of the test passed without an error.

TODO

• Explain motivation or link existing issue(s)
• Test changes and document test plan
• Update documentation as needed
• Update changelog as needed

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.8%. Comparing base (bfcd746) to head (8f4496b).

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6570   +/-   ##
=======================================
  Coverage     79.7%   79.8%           
=======================================
  Files          355     355           
  Lines        47168   47179   +11     
=======================================
+ Hits         37615   37663   +48     
+ Misses        7408    7371   -37     
  Partials      2145    2145           

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[ivan4th]

See #6573 which fixes the underlying problem