Move request_and_transport to the Client

This patch moves the `_get_transport` and `request_and_transport` method
to the client. Both method are useful for other resources like Message,
for example.

This patch also moves the is_functional logic to the BaseTest class and
splits unittests from functional tests.

Partially-Implements: python-marconiclient-v1
Change-Id: Iaf56c234291b355c98817feee5644a5dd07c0b7f
Merge "Move request_and_transport to the Client"