(QENG-1033) Don't modify constants and properly support all Linux platforms in Perf

The current implementation allows non-Linux Beaker SUTS to be included in a run with performance gathering. In this scenario, we have to do the Right Thing by ignoring non-Linux hosts.

unelss host['platform'] =~ /sles-/

Would potentially allow the following code to run on Windows, AIX, OS X, etc...