Implement a 120s timeout in case lctl process is taking too long

[RDruon]

Demo below is using a timeout of 5s (instead of 120s from this PR):

[root@node ~]# RUST_LOG=debug ./lustrefs-exporter --port 34221
2024-09-06T15:49:34.617893Z  INFO lustrefs_exporter: Listening on http://0.0.0.0:34221/metrics
2024-09-06T15:49:41.238172Z DEBUG lustrefs_exporter: lctl jobstats timed out

[root@es18kxe-co-vm07 ~]# time curl http://localhost:34221/metrics | tail
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 75.1M    0 75.1M    0     0  15.0M      0 --:--:--  0:00:05 --:--:-- 16.7M
lustre_job_stats_total{operation="getattr",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="setattr",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="punch",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="sync",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="destroy",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="create",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="statfs",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="get_info",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="set_info",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0
lustre_job_stats_total{operation="quotactl",component="ost",target="testfs-OST0003",jobid="SLURM_JOB199002:0:client"} 0

real    0m5.014s
user    0m0.883s
sys     0m1.449s

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 91.53%. Comparing base (fbb9f54) to head (181d1fd).

Files with missing lines	Patch %	Lines
lustrefs-exporter/src/main.rs	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #77      +/-   ##
==========================================
- Coverage   91.73%   91.53%   -0.20%     
==========================================
  Files          41       41              
  Lines        5228     5236       +8     
  Branches     5228     5236       +8     
==========================================
- Hits         4796     4793       -3     
- Misses        397      405       +8     
- Partials       35       38       +3     

Flag	Coverage Δ
2_14_0_ddn133	35.26% <ø> (ø)
2_14_0_ddn145	36.01% <ø> (ø)
all-tests	91.53% <0.00%> (-0.20%)	⬇️

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[github-actions]

Benchmark for 00d91d7

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Test	Base	PR	%
jobstats 100	4.4±0.79ms	4.7±0.96ms	+6.82%
jobstats 1000	42.2±6.69ms	46.0±7.90ms	+9.00%

[github-actions]

Benchmark for 1933e6a

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Test	Base	PR	%
jobstats 100	4.4±0.82ms	4.4±0.84ms	0.00%
jobstats 1000	44.9±8.17ms	43.3±7.94ms	-3.56%