ftracetest: Add kprobes on ftrace testcase

Add a kprobes on ftrace testcase. The testcase verifies that
- enabling and disabling function tracing works on a function which
  already contains a dynamic kprobe
- adding and removing a dynamic kprobe works on a function which is
  already enabled for function tracing

Link: http://lkml.kernel.org/p/1413802323-5297-2-git-send-email-heiko.carstens@de.ibm.com
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>