60e17d2822
When user used the trace print command from docs/tracing.txt: ./scripts/simpletrace.py trace-events trace-* the user maybe be misled by the "trace-*", because if user directly copy the comand line to run, there alway print the bored message: "usage: ./scripts/simpletrace.py <trace-events> <trace-file>" then we should describe that the "trace-*" represented. Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>