Add a unit test coverage tox job

This commit adds a new tox job for running the tempest unit tests with
coverage enabled.

Change-Id: I36b5390ffd241e08e40be2d4b92b9e91a71cdc9e
Fix an error when executing run_tests.sh

In the recent commit I1473fe4da96aecd0b3b0bf3a3ec1e3e87039271b , the
coverage option was introduced. But there are a few typos in the shell
script.
This commit fixes it.

Change-Id: Iecdd72f730c0f0971424ca48e6f122481493b1ee
Closes-Bug: #1268808
Add more console output log for scenario tests

- Generalize _log_console_output
- Added console log ouput for ssh or ping check

Change-Id: I2900a64de4ea2ce447cb41c3b0290aa3186098e2
Merge "Add more console output log for scenario tests"
Merge "Add a unit test coverage tox job"
Merge "Fix an error when executing run_tests.sh"