Use setup.py testr to run testr in run_tests.sh.

Using the setup.py testr command in run_tests.sh will sync run_tests.sh
up with the way tox currently runs the tests and collects coverage.

Change-Id: I21e3965280b3242a860c6be49c4dca44f197b03a
Fix the wrong datatype in task_log table.

    Change period_begining and period_ending to Datetime type.
    Add the migration script.

Change-Id: Ic5d61d6e7e847a1943825a0cb342b0b015bc0b70
Fixes: bug #1102477
Merge "Fix the wrong datatype in task_log table."
Merge "Use setup.py testr to run testr in run_tests.sh."