perf probe: Fix a segfault when removing uprobe events

perf probe: Fix a segfault when removing uprobe events

Fix a segfault bug and a small mistake in perf probe -d.

Since the "ulist" in perf_del_probe_events is never initialized,
strlist__add(ulist, *) always causes a segfault when removing
uprobe events by perf probe -d.

Also, the "str" local variable is never released if fail to
allocate the "klist". This fixes it too.

This has been introduced by the commit e607f1426b58 ("perf probe:
Print deleted events in cmd_probe()").

Reported-by: Milian Wolff <milian.wolff@kdab.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20150916125241.4446.44805.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>