PerfMonComps: Short-term workaround for missing psutil in LCG 97a_ATLAS_1

The psutil module is missing in LCG 97a_ATLAS_1. Currently PerfMonMTSvc gets the application start time using that module and this causes the issue raised in [1]. This MR essentially provides a workaround to this problem such that we can recover performance related metrics in jobs w/ threads>1. A more proper way of handling dependencies will be implemented in a future MR such that we catch similar issues at build time. Also, we'll need to eventually include the module in a future LCG release and/or find another way to extract that information (which can also be done on the C++ side, of course).

[1] ATLASRECTS-5592