`update_vars` and `set_vars` were removed from `ansible_manager`

It is not necessary to update var files. We only need (and have to) to set them.
inventory option was added for testrunner and some small changes:

* code style fixes
* usage of OS_HOSTNAME_PREFIX in not proper places was removed
* fix for rebuild bug was corrected
* `collect_instances_params` method was moved to another module and renamed
Test configuration files were updated.
Merge pull request #44 from 'features/runner-inventory'

inventory option was added for testrunner and some small changes