tracing: Change trace event sample to use strlcpy instead of strncpy

Strings should be copied with strlcpy instead of strncpy when they will
later be printed via %s. This guarantees that they terminate with a
NUL '\0' character and do not run pass the end of the allocated string.

This is only for sample code, but it should stil represent a good
role model.

Link: http://lkml.kernel.org/p/51C2E204.1080501@huawei.com



Signed-off-by: Zhao Hongjiang <zhaohongjiang@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>