fix: create errors from non-constant strings

[europaul]

Since go 1.24 vet reports the usage of non-constant strings in Printf as errors (see https://tip.golang.org/doc/go1.24#vet). This change fixes the found occurrences in our tests.

Example:

./nw_test.go:91:21: non-constant format string in call to fmt.Errorf

This fix is mostly relevant for local builds as we are not yet using go 1.24 in the CI, but the nature of the issue itself is independent of the go version used.

[Copilot]

PR Overview

This PR addresses Go 1.24 vet issues by replacing fmt.Errorf calls with errors.New so that error messages are built from constant strings. It also includes a change in logging in tests/vcom/vcom_test.go to call Log instead of Logf.

• Updated tests/vcom/vcom_test.go to use logT.Log.
• Replaced fmt.Errorf with errors.New in tests across network, app, volume, docker, and lim packages.
• Ensured that error message construction complies with constant string requirements per Go 1.24 vet.

Reviewed Changes

File	Description
tests/vcom/vcom_test.go	Changed logT.Logf to logT.Log to avoid non-constant formatting usage.
tests/network/nw_test.go	Replaced fmt.Errorf with errors.New for building error messages.
tests/app/app_test.go	Replaced fmt.Errorf with errors.New in error returns.
tests/volume/vol_test.go	Replaced fmt.Errorf with errors.New in error returns.
tests/docker/docker_test.go	Replaced fmt.Errorf with errors.New in error handling of HTTP responses.
tests/lim/lim_test.go	Replaced fmt.Errorf with errors.New in test assertions.

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

tests/vcom/vcom_test.go:41

• Verify that switching from logT.Logf to logT.Log preserves the intended output formatting, especially if additional formatting was expected.

logT.Log(out)

tests/network/nw_test.go:88

• [nitpick] The error message string is initialized with a leading newline, which may result in unexpected formatting of error messages. Consider removing the initial newline unless it is intentionally required.

out := "\n"

[europaul]

@uncleDecart could you please restart the failed tests? I think they are just being flaky

[eriknordmark]

LGTM