Unactionable error message spam

[tgoodsell-tempus]

Expected behavior:
This error doesn't appear if it's not something we're able to remediate.

Current behavior:
Seeing this error spammed in our auth / proxy cluster:

{
caller: "srv/usermgmt.go:469"
component: null
level: "error"
message: "Error during temporary user cleanup: cant find getent binary
	exec: "getent": executable file not found in $PATH"
timestamp: "2024-05-22T18:49:04Z"
}

Bug details:

• Teleport version: public.ecr.aws/gravitational/teleport-ent-distroless:15.1.9
• Recreation steps: Unknown, appears to have started once we cutover to the distroless images.

[webvictim]

Came here to report this too; this is because the distroless images don't have the getent binary available (similar to the lack of hostname which is fixed by #42104)