perf tests: Fix hist accumulation test

perf tests: Fix hist accumulation test

User's values from .perfconfig could overload the default callchain
setup and cause this test to fail.  Making sure the test is using
default callchain_param values.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1467634583-29147-3-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>