lisa.tests.cpufreq.sanity: Use separate res_dir for each sysbench invocation
lisa.tests.cpufreq.sanity: Use separate res_dir for each sysbench invocation

Avoid overwriting output.log files when using a single res_dir. Fix that by
making a separate res_dir for each invocations.

ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa,ARM-software/lisa