tools lib traceevent: Handle strdup failure cases

There were some places didn't check return value of the strdup and had
unneeded/duplicated checks.  Fix it.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/1333940074-19052-5-git-send-email-namhyung.kim@lge.com


Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>