Move `./run_tests.sh` to Oslo

Moved Nova `./run_tests.sh` script to `tools/run_tests_common.sh` file.
This script run unit-tests and can be reused in other projects.
Added script `./run_tests.sh` with project specific variables to run
`tools/run_tests_common.sh` script.
Added required `tools/*` files for pretty colorizer outpoot.
Modified `tests/utils.py` file - added work with OS_TEST_TIMEOUT,
OS_STDOUT_CAPTURE and OS_STDERR_CAPTURE environment variables from .testr.conf

blueprint run-tests-script

Change-Id: I057e8cf2c74d160402cb881fc761623c74905b7e
Merge "Move `./run_tests.sh` to Oslo"