Maintenance mode improvements

[fyrchik]

1. Allow to specify mode: disabled in the configuration.
2. Use blobstor paths as an identifier for a shard.

[codecov]

Codecov Report

Merging #1840 (22e69f9) into master (b2aa994) will decrease coverage by 0.07%.
The diff coverage is 40.59%.

❗ Current head 22e69f9 differs from pull request most recent head a4bc317. Consider uploading reports for the commit a4bc317 to get more accurate results

@@            Coverage Diff             @@
##           master    #1840      +/-   ##
==========================================
- Coverage   31.32%   31.24%   -0.08%     
==========================================
  Files         374      375       +1     
  Lines       26495    26510      +15     
==========================================
- Hits         8300     8284      -16     
- Misses      17507    17535      +28     
- Partials      688      691       +3     

Impacted Files	Coverage Δ
cmd/neofs-node/config.go	0.00% <0.00%> (ø)
pkg/local_object_storage/blobstor/blobstor.go	79.16% <ø> (ø)
pkg/local_object_storage/blobstor/info.go	0.00% <0.00%> (ø)
pkg/services/control/types.go	75.51% <ø> (-0.97%)	⬇️
pkg/services/control/types.pb.go	30.46% <16.27%> (-2.88%)	⬇️
cmd/neofs-node/config/engine/config.go	86.20% <60.00%> (-5.80%)	⬇️
pkg/services/control/types_neofs.pb.go	69.00% <76.47%> (+0.76%)	⬆️
pkg/local_object_storage/engine/control.go	71.85% <93.33%> (+1.08%)	⬆️
...ct_storage/blobstor/blobovniczatree/blobovnicza.go	64.19% <100.00%> (+3.43%)	⬆️
pkg/local_object_storage/blobstor/fstree/fstree.go	68.39% <100.00%> (+1.53%)	⬆️
... and 15 more

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