tools lib traceevent: Handle possible strdup() error in tep_add_plugin_path() API

tools lib traceevent: Handle possible strdup() error in tep_add_plugin_path() API

Free allocated resources and return -1 in case strdup() fails in
tep_add_plugin_path() API.

Link: https://lore.kernel.org/r/CAM9d7chfvJwodpVrHGc5E2J80peRojmYV_fD8x3cpn9HFRUw2g@mail.gmail.com
Link: https://lore.kernel.org/linux-trace-devel/20200714103027.2477584-9-tz.stoyanov@gmail.com
Link: https://lore.kernel.org/linux-trace-devel/20200716092014.2613403-9-tz.stoyanov@gmail.com
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200722011755.720803193@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>