Implement tests for packages with 0.00% coverage

[ayuryshev]

$ go test ./pkg/... -cover -list "Example*|Test*"  | grep "no test files"
# ?       github.com/skycoin/skywire/pkg/route-finder/client      [no test files]
# ?       github.com/skycoin/skywire/pkg/util/pathutil    [no test files]
$ go test ./internal/... -cover -list "Example*|Test*"  | grep "no test files"
# ?       github.com/skycoin/skywire/internal/httputil    [no test files]
# ?       github.com/skycoin/skywire/internal/pathutil    [no test files]

Implement at least 1 test in packages:

• github.com/skycoin/skywire/pkg/route-finder/client
• github.com/skycoin/skywire/pkg/util/pathutil
• github.com/skycoin/skywire/internal/httputil
• github.com/skycoin/skywire/internal/pathutil