fix modbus-tcp change server to client config crash.

[moruoxian]

default client mode ，then change to server mode，then change to client mode the progress crash. Release the corresponding IP memory according to the current

[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.77778% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.17%. Comparing base (60ef477) to head (9c98e07).
⚠️ Report is 164 commits behind head on main.

Files with missing lines	Patch %	Lines
plugins/modbus/modbus_tcp.c	77.77%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2549      +/-   ##
==========================================
- Coverage   66.68%   66.17%   -0.52%     
==========================================
  Files         121      120       -1     
  Lines       27568    27512      -56     
==========================================
- Hits        18385    18205     -180     
- Misses       9183     9307     +124     

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