run: check for netperf version in user environment

For native Genode netperf port.
run: split native Genode netperf script

Split the netperf run script into 3 ones so that it can be used more easily
in an automated run.

netperf.run        - use native nic driver (x86) or usb2.0 (arndale, panda)
netperf_usb30.run  - use native nic driver (x86) or usb3.0
netperf_bridge.run - use native nic driver (x86) or usb3.0 (arndale) and bridge
run: check for netperf version in user environment

For L4linux version on foc_arndale.
run: split netperf l4linux script

Split the netperf run script into 3 ones so that it can be used more easily
in an automated run.

It is solely for foc_arndale by now.

l4linux_netperf.run        - use nic via usb2.0
l4linux_netperf-usb30.run  - use nic via usb3.0
l4linux_netperf-bridge.run - use nic via usb3.0 + bridge
run: prepare netperf l4lx output for post processing
run: add netperf tests to autopilot list

* native Genode (using lwIP) netperf
as
* L4Linux netperf