Fix crash caused by receiving #append_entries_reply{success=false} from unknown peer

[sile]

Proposed Changes

This PR fixes a ra server process (leader) crash caused by receiving a #append_entries_reply{success=false} message from an unknown peer.

Types of Changes

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• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (correction or otherwise)
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• I have added tests that prove my fix is effective or that my feature works
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Further Comments

If the patch in this PR is not applied, the following crash log will be generated by the append_entries_reply_no_success_from_unknown_peer test case.

=== Location: [{ra_server,handle_leader,472},
              {ra_server_SUITE,append_entries_reply_no_success_from_unknown_peer,989},
              {test_server,ts_tc,1794},
              {test_server,run_test_case_eval1,1303},
              {test_server,run_test_case_eval,1235}]
=== === Reason: no match of right hand side value 
                 #{{n1,'ct_ra@localhost'} =>
                       #{status => normal,next_index => 1,match_index => 0,
                         query_index => 0,commit_index_sent => 0}}
  in function  ra_server:handle_leader/2 (src/ra_server.erl, line 472)
  in call from ra_server_SUITE:append_entries_reply_no_success_from_unknown_peer/1 (test/ra_server_SUITE.erl, line 989)
  in call from test_server:ts_tc/3 (test_server.erl, line 1794)
  in call from test_server:run_test_case_eval1/6 (test_server.erl, line 1303)
  in call from test_server:run_test_case_eval/9 (test_server.erl, line 1235)

[kjnilsson]

thank you @sile !

[sile]

👍