Add Neutron benchmarks scenario for creating and listing ports

Scenario NeutronNetworks.create_and_list_ports is added, which does the following:
  - creates network
  - creates a given number of ports
  - lists ports

blueprint benchmark-scenarios-for-neutron

Change-Id: I029f220dd70beb0c248877bd4bd718dfa63aba40
small fixes on rest/base.py

- rename a base class from FunctionalTest to PecanControllerTest which
makes this naming more accurate
- remove some print statement for debug uses
- use _request_json in delete method
- use requests module instead of six.moves.urllib

Change-Id: I4463466bab91ad538295668b9e8133a1a1f99caa
Adding Image Context Class

This Context Class implements Image Context Subclass
to Benchmarking Mechanism. This also adds a simple list_image benchmark
scenario which tests glance image-list command

bp benchmark-context-image

Change-Id: I272a36cebb568e8d599ebd65beb53b6a2c628b6e
Merge "small fixes on rest/base.py"
Merge "Add Neutron benchmarks scenario for creating and listing ports"
Merge "Adding Image Context Class"
Periodic runner refactoring

    'preiodic' ranner renamed to rps (runs per second).
    Extensible pool of multiprocessing.Process was implemented instead
    of using constant length multiprocessing.Pool. That should decrease memory
    usage on large iterations and related errors.

Change-Id: I6e367ea30d89d5d0e7ba212ed22e8658421ac9bd