fix: worker: don't log normal storage stat calls

[magik6k]

Currently we print logs like

2022-05-27T19:46:05.586+0200    INFO    stores  stores/local.go:160     storage stat    {"took": 0.000045108, "reservations": 0}
2022-05-27T19:46:05.586+0200    INFO    stores  stores/local.go:160     storage stat    {"took": 0.000022857, "reservations": 0}
2022-05-27T19:46:05.586+0200    INFO    stores  stores/local.go:160     storage stat    {"took": 0.000016145, "reservations": 0}
2022-05-27T19:46:05.586+0200    INFO    stores  stores/local.go:160     storage stat    {"took": 0.000016495, "reservations": 0}

On all workers for each storage path every ~10s. This is extremely spammy, especially in larger setups with many workers and many storage paths

[codecov]

Codecov Report

Merging #8744 (a448b22) into master (44d415a) will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #8744      +/-   ##
==========================================
+ Coverage   40.92%   40.94%   +0.01%     
==========================================
  Files         692      692              
  Lines       76252    76253       +1     
==========================================
+ Hits        31209    31223      +14     
+ Misses      39681    39655      -26     
- Partials     5362     5375      +13     

Impacted Files	Coverage Δ
extern/sector-storage/stores/local.go	60.40% <0.00%> (-1.18%)	⬇️
chain/events/observer.go	73.79% <0.00%> (-6.21%)	⬇️
extern/storage-sealing/currentdealinfo.go	71.92% <0.00%> (-3.51%)	⬇️
chain/types/tipset_key.go	85.96% <0.00%> (-3.51%)	⬇️
extern/sector-storage/sched_assigner_common.go	78.40% <0.00%> (-2.28%)	⬇️
storage/wdpost_run.go	70.59% <0.00%> (-1.36%)	⬇️
miner/miner.go	56.06% <0.00%> (-1.32%)	⬇️
blockstore/autobatch.go	57.14% <0.00%> (-0.85%)	⬇️
chain/sync_manager.go	73.91% <0.00%> (-0.63%)	⬇️
... and 12 more