selftests/ftrace: Update test for more eprobe removal process

The removal of eprobes was broken and missed in testing. Add various ways
to remove eprobes that are considered acceptable to the testing process to
catch when/if they break again.

Link: https://lkml.kernel.org/r/20211013205533.836644549@goodmis.org



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