Lower snapshot listing interval

[mkpankov]

Listing times on the agent. With 10 snapshots:

[root@mds1 vagrant]# time iml-agent snapshot list fs
{{[Snapshot
{ filesystem_name: "fs", snapshot_name: "test2", snapshot_fsname: "7941fd0f", modify_time: 2020-09-25T09:53:04Z, create_time: 2020-09-25T09:53:04Z, mounted: Some(false), comment: Some("") }
...
real 0m4.728s
user 0m0.610s
sys 0m0.408s

With 20 snapshots:

[root@mds1 vagrant]# time iml-agent snapshot list fs
[Snapshot
{ filesystem_name: "fs", snapshot_name: "test2", snapshot_fsname: "7941fd0f", modify_time: 2020-09-25T09:53:04Z, create_time: 2020-09-25T09:53:04Z, mounted: Some(false), comment: Some("") }
...
real 0m11.720s
user 0m1.571s
sys 0m0.905s

There's also some variance. For 20 snapshots, these are 5 times: 0m11.720s, 0m10.119s, 0m9.724s, 0m10.353s, 0m8.728s.

Signed-off-by: Michael Pankov work@michaelpankov.com

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This change is 

[ip1981]

What about 1000? :)

I think we'll need to update the snapshot table on each snapshot event (creation, removal) anyway for better UX.

[jgrund]

What about 1000? :)

Currently due to other limitations, lctl snapshot_list won't print anything past 100 snapshots.