Avoid to re-establish replication if node is already myself primary in CLUSTER REPLICATE

[enjoy-binbin]

If n is already myself primary, there is no need to re-establish the replication connection.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 70.57%. Comparing base (39f8bcb) to head (eb3ef43). :warning: Report is 821 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable     #884      +/-   ##
============================================
- Coverage     70.62%   70.57%   -0.05%     
============================================
  Files           112      112              
  Lines         61509    61512       +3     
============================================
- Hits          43440    43412      -28     
- Misses        18069    18100      +31     

Files with missing lines	Coverage Δ
src/cluster_legacy.c	85.62% <100.00%> (+0.33%)	:arrow_up:

... and 10 files with indirect coverage changes

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[enjoy-binbin]

I am merging this since #885 is merged, see top comment for more details