fix: decrement requests count in case of exception inside HeadRuntime

[JoanFM]

In case of some Exceptions, the count of pending requests and some stats related were not properly decremented

[girishc13]

LGTM
Please update the title and description.

[codecov]

Codecov Report

Merging #5383 (9b8b714) into master (de53f95) will increase coverage by 0.10%.
The diff coverage is 98.12%.

@@            Coverage Diff             @@
##           master    #5383      +/-   ##
==========================================
+ Coverage   86.83%   86.94%   +0.10%     
==========================================
  Files         100      101       +1     
  Lines        6512     6611      +99     
==========================================
+ Hits         5655     5748      +93     
- Misses        857      863       +6     

Flag	Coverage Δ
jina	86.94% <98.12%> (+0.10%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
jina/parsers/deprecated.py	83.33% <ø> (ø)
jina/parsers/orchestrate/pod.py	100.00% <ø> (ø)
jina/parsers/orchestrate/runtimes/head.py	100.00% <ø> (ø)
jina/parsers/orchestrate/runtimes/remote.py	100.00% <ø> (ø)
jina/parsers/orchestrate/runtimes/runtime.py	100.00% <ø> (ø)
jina/serve/streamer.py	95.91% <ø> (ø)
jina/serve/runtimes/head/request_handling.py	94.11% <94.11%> (ø)
jina/orchestrate/flow/base.py	90.77% <100.00%> (ø)
jina/parsers/orchestrate/runtimes/worker.py	100.00% <100.00%> (ø)
jina/serve/executors/decorators.py	98.71% <100.00%> (+0.18%)	⬆️
... and 9 more

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