testnode: Fix statement in unit test case (runner.runTestSuite)
testnode: Add getting Slapos Master Url (for scalability)
scalability: runScalabilityTestSuite: Change the way to launch suite

Launch one tester per test.
scalability: runScalabilityTestSuite: remove failed docs counting
scalability: runScalabilityTestSuite: Restructure code.
test_node: ScalabilityTestRunner: Fix typo

Noticed by Cédric de Saint Martin.