perf test: Fix return values checking

Fixing some cut'n'paste mistakes.

LKML-Reference: <20110124233900.GA3443@epc900.nay.redhat.com>
Signed-off-by: Han Pingtian <phan@redhat.com>
[ committer note: I had already removed the CPU_ALLOC calls ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>