Changes

tests/linux: remove a confusing warning
"Cannot force linux component first because HWLOC_COMPONENTS
environment variable is already set to linux,stop"
This was caused by us setting HWLOC_COMPONENTS to avoid lstopo --if
fsroot letting the pci backend annotate things. Stop using --if fsroot
and rely on envvars instead.
Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>