Run unittests using nose instead of run_tests.sh (testr)

Using community's testr cause import sequence errors sometimes. Most
stable way seems to be run test using nose.
Also use coverage to gather coverage statistics.

Change-Id: I1e8322aecd504f990f8e3b075d8bc4d389eeaef0
Merge "Run unittests using nose instead of run_tests.sh (testr)"