Small cleanup for initial TUF rollout

[RebeccaMahany]

Relates to #954.

Makes code review changes from #1268.

Future work + linked PRs

Subsequent PRs will tackle the following (order is not set in stone):

1. Devices on beta channel use new autoupdate library
2. Devices on stable channel use new autoupdate library
3. Ship a more up-to-date TUF repo
4. Report new version to K2 after update
5. An "update now" functionality tied to control server
6. Eventually removing the old notary autoupdater

Previous work:

1. Run new TUF autoupdater side-by-side with notary autoupdater #1081
2. Expose data and metrics about new TUF autoupdater #1103
3. Point to production TUF infra #1108
4. Perform retry on TUF update #1110
5. Add library manager to handle TUF downloads #1111
6. Small autoupdate improvements #1119
7. Pass knapsack in to tuf autoupdater to simplify configuration #1168
8. [TUF autoupdater] Remove osquery client dependency #1178
9. Move TUF test setup to new package #1188
10. [TUF autoupdater] Check out latest #1185
11. [TUF autoupdater] Include arch in release file path and download file path #1195
12. [TUF] Keep staging directory clean #1270
13. [TUF autoupdater] Devices on nightly channel use new autoupdate library #1268

[directionless]

Thank you. There's another one several lines down

[RebeccaMahany]

Pushed an update to remove the strings.HasSuffix check since strings.TrimSuffix is a no-op if the suffix isn't present -- unless you meant a different one and I'm missing it?

[directionless]

launcher/pkg/autoupdate/findnew.go

Lines 334 to 337 in dec53eb

	installedPath := os.Getenv(LegacyAutoupdatePathEnvVar)
	if installedPath != "" {
	path = installedPath
	}