provide ability to tweak oslo log defaults

Before we parse the config object, rewrite the oslo log levels to
include defaults that make more sense for tempest. Based off a
similar approach done in keystone.

Change-Id: I7002d9fc3997817d1f07547404aadb011965f472
Revert "don't reuse servers in test_server_actions"

This reverts commit b7f648b31c9044e3a7c25c0fb1dcc31a81e0da9f.

Change-Id: I31672c8b131fec4a916c4d703f6819c22d605876
Related-Bug: #1298472
Merge "Revert "don't reuse servers in test_server_actions""
Merge "provide ability to tweak oslo log defaults"