Handle 'not supported' in quota_slave.acct_*

[RDruon]

quota_slave.acct_* can show not supported instead of YAML blob, this patch handles this.

osd-ldiskfs.lustre-MDT0000.quota_slave.acct_project=not supported
osd-ldiskfs.lustre-MDT0000.quota_slave.acct_user=
usr_accounting:
- id:      0
  usage:   { inodes:          378, kbytes:     20375648 }
- id:      1339
  usage:   { inodes:          167, kbytes:        12164 }

[RDruon]

Shown here

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.77%. Comparing base (fe11f85) to head (a899f2b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #85   +/-   ##
=======================================
  Coverage   91.77%   91.77%           
=======================================
  Files          41       41           
  Lines        5225     5238   +13     
  Branches     5225     5238   +13     
=======================================
+ Hits         4795     4807   +12     
  Misses        394      394           
- Partials       36       37    +1     

Flag	Coverage Δ
2_14_0_ddn133	35.48% <100.00%> (+0.21%)	⬆️
2_14_0_ddn145	36.21% <95.45%> (+0.19%)	⬆️
all-tests	91.77% <100.00%> (+<0.01%)	⬆️

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[github-actions]

Benchmark for 4253055

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Test	Base	PR	%
jobstats 100	3.6±0.43ms	3.9±0.62ms	+8.33%
jobstats 1000	37.7±4.72ms	37.6±5.29ms	-0.27%

[github-actions]

Benchmark for d02541f

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Test	Base	PR	%
jobstats 100	3.8±0.63ms	3.8±0.54ms	0.00%
jobstats 1000	37.0±4.73ms	37.0±4.43ms	0.00%

[github-actions]

Benchmark for 790581a

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Test	Base	PR	%
jobstats 100	3.9±0.62ms	3.9±0.63ms	0.00%
jobstats 1000	36.9±3.99ms	37.1±4.75ms	+0.54%

[github-actions]

Benchmark for 32b5742

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Test	Base	PR	%
jobstats 100	3.7±0.48ms	3.9±0.61ms	+5.41%
jobstats 1000	38.6±5.07ms	38.7±4.66ms	+0.26%

[github-actions]

Benchmark for 1eaea95

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Test	Base	PR	%
jobstats 100	3.8±0.59ms	3.7±0.50ms	-2.63%
jobstats 1000	37.5±4.63ms	37.9±5.33ms	+1.07%

[github-actions]

Benchmark for 55d30c0

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Test	Base	PR	%
jobstats 100	3.8±0.59ms	3.7±0.49ms	-2.63%
jobstats 1000	40.1±5.66ms	37.1±4.97ms	-7.48%