trace-cmd: Close the tracing_on_fd descriptor when deleting an instance
trace-cmd: Close the tracing_on_fd descriptor when deleting an instance

When a instance directory is about to be removed, close the
tracing_on_fd descriptor for it to prevent that from causing a
-EBUSY error on removing the directory.

Signed-off-by: Steven Rostedt <43232e92d70cc7aa53504ad0397085ee47bad87f@goodmis.org>

bigzz/trace-cmd,bigzz/trace-cmd