selftests/ftrace: Update kprobe event error testcase

Update kprobe event error testcase to test if it correctly
finds the exact same probe event.

Link: http://lkml.kernel.org/r/156879695513.31056.1580235733738840126.stgit@devnote2



Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>