Netconf Scaling test for multithreaded GET requests

This test suite first emits a batch of "single device mount"
requests to the netconf (via restconf), then executes a wait
loop on each of them (to ensure each of them is connected)
and then uses a Python tool to issue a GET requests for
config data on them. Each device gets one request for its
config data but there are multiple requests being made
concurrently (the count of these concurrent requests is
configurable via a Robot variable). Then it finally issues a
batch of "deconfigure single device" requests. A link to a
known bug is also included as especially the "deconfigure"
part of the test appears to be hit by it pretty badly.

Change-Id: I924d9a72921d29580d54fcf0317aec4137174fb2
Signed-off-by: Jozef Behran <jbehran@cisco.com>