Fix various alerts reported by LGTM

[danielealbano]

This PR fixes various alerts reported by LGTM to improve the overall code quality score

[codecov]

Codecov Report

Merging #145 (d3e6be5) into main (802524d) will increase coverage by 0.08%.
The diff coverage is 61.90%.

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
+ Coverage   80.27%   80.35%   +0.08%     
==========================================
  Files          86       86              
  Lines        5180     5191      +11     
==========================================
+ Hits         4158     4171      +13     
+ Misses       1022     1020       -2     

Impacted Files	Coverage Δ
src/protocol/redis/protocol_redis_reader.c	92.59% <ø> (-0.06%)	⬇️
src/worker/storage/worker_storage_iouring_op.c	87.50% <ø> (ø)
src/storage/db/storage_db.c	48.48% <50.00%> (+0.29%)	⬆️
src/worker/worker.c	81.13% <50.00%> (ø)
src/hugepage_cache.c	93.75% <100.00%> (ø)
src/protocol/redis/protocol_redis_writer.c	60.73% <100.00%> (-0.90%)	⬇️
src/spinlock.c	100.00% <100.00%> (ø)
src/storage/channel/storage_channel.c	100.00% <100.00%> (ø)
src/support/simple_file_io.c	92.30% <100.00%> (-7.70%)	⬇️
... and 2 more

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[lgtm-com]

This pull request fixes 16 alerts when merging d3e6be5 into 802524d - view on LGTM.com

fixed alerts:

• 7 for Missing return statement
• 4 for Expression has no effect
• 3 for Comparison result is always the same
• 2 for Duplicate include guard