Unittests refactoring for ci

Logic that supports automated execution of unit tests for ci purpose
were added via setUp/tearDownPackage functions in
testing/tests/__init__.py file. Now when tests started via nose in
package setUp function nailgunmimic server is setting up in separate
process and terminating in tearDown. This functionality provides unified
way to execute unit tests.

Change-Id: I4a033757c8d902c90b0a6c7eb54c1511ab721f99