selftests/ftrace: Replace \e with \033

The \e sequence character is not POSIX. Fix that by using \033 instead.

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Shuah Khan <shuah@kernel.org>