trace-cmd: The extract command should not block
trace-cmd: The extract command should not block

The extract command is used to pull data out of the ring buffer.
It should not block on reads, as it is not used to wait for data.
It is only used to pull out existing data.

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

bigzz/trace-cmd,bigzz/trace-cmd