tools lib traceevent: Fix bad force_token escape sequence

Older kernels have a bug that creates invalid symbols. event-parse.c
handles them by replacing them with a "%s" token. But the fix included
an extra backslash, and "\%s" was added incorrectly.

Signed-off-by: Michael Sartain <mikesart@fastmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20180112004821.827168881@goodmis.org
Link: http://lkml.kernel.org/r/d320000d37c10ce0912851e1fb78d1e0c946bcd9.1497486273.git.mikesart@fastmail.com


Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>