Move the statusTxtContent to fix this confusing error
when running `go get github.com/rfjakob/gocryptfs/...`:
$ go get github.com/rfjakob/gocryptfs/...
# github.com/rfjakob/gocryptfs/tests/example_filesystems
tests/example_filesystems/example_test_helpers.go:22:16: undefined: statusTxtContent
tests/example_filesystems/example_test_helpers.go:75:16: undefined: statusTxtContent