(QENG-807) Add performance/load gathering to beaker

This PR adds sysstat output for all the Linux hosts after a beaker run. To enable, add --collect-perf-data to the beaker command line. It is a nullop if --collect-perf-data is not used and is a nullop on hosts that are not Linux platforms. By using --collect-perf-data, the sysstat package will be installed on the Linux hosts.
Instead of the list, how about `if host['platform'] !~ /sles/`