Add neutron quotas management in benchmark context

This patch allows to modify quotas related to neutron for
generated benchmark's tenants by extended the context object,
allowing to run large scale scenarios.

Also correct some copy/paste error in cinder/nova quotas tests.

Blueprint benchmark-context-tenant-quotas

Change-Id: Ib588e6fdf8cdd5c81cefaa4555c437cfaf92fad7
Merge "Add neutron quotas management in benchmark context"
Add multihost engine

This engine deploy multihost config with existing engines.

blueprint multihost-deploy

Change-Id: Id18748dce7a47dd635e039497f7bd8eaf3ca99df
Add number and file validators

 * number: Check a numeric argument specifying min, max. Optionally
           require input to be integer.
 * file_exists: Check that a file exists and can be opened

 These validators are used in the runcommand in instance benchmark
 (patch pending)

Change-Id: Ia12e95b3661c97ae6f4c54caf44fdf33b72aa736
Create vm benchmark module

Move the run command in instance benchmark out of the nova module into
its own module (vm). Functionality is then split into a scenario module
and a utils module, following the structure of the other benchmarks.

Tests are also refactored.

Change-Id: Ida26b5047b8e76f72e34c2aab9b8ab94f46bbad6