Replace Bierman02 with RFC8040 for OpenFlow Plugin

Replace Bierman02 with RFC8040 for OpenFlow Plugin

Create new variables for RFC8040 topology & inventory API URLs
for OpenFlow Plugin test suites and replace RESTCONF APIs
based on Bierman02 with the ones for RFC8040.

Some of the common libraries in 'csit/libraries' used by OpenFlow
Plugin test suites are also updated. This requires additional
changes in other test suites using the updated libraries.

HEADERS_YANG_JSON variable is temporarily changed from
'application/yang.data+json' to 'application/json' to make
it compatible for both Bierman02 & RFC8040 - the former
is not accepted by RFC8040 URLs.

Add a step to break out of request loop in ScaleClient.py
if there are many request timeout exceptions (more than 10)
and a step to check if there is RuntimeException in the
controller log after checking NPE in WorflowsOpenFlow.robot
and WorflowsL2switch.robot - using RFC8040 triggered
RuntimeException because of the circuit breaker timeout
issue (CONTROLLER-2026) making overall test fail to complete
(or take too long).

Signed-off-by: Sangwook Ha <sangwook.ha@verizon.com>
Signed-off-by: Sandhiya Selvaraj <sandhiya.selvaraj@verizon.com>
Change-Id: I25625598e5eb7aedac7d5a0b536af8ac26a9ebf7