Write tests output to stdout

This allows to watch test progress, in color.

Change-Id: I7ceebddae420d7d942f70a6b74ee0a3d11cf105e
Refs: bug #1187912
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.

Cherry-picked with certain corrections from 7ff4b3855.

Change-Id: I1e8322aecd504f990f8e3b075d8bc4d389eeaef0