dockertest.subtest: Improve the (sub)test log output

This patch gets rid of standard autotest logging and uses the python
logging functions instead (as it's usual in autotest tests itself!).

Each line is prepended with 2 tabs in order to improve readability of
the text. Additionally duplicite messages were removed and the SubSubtest
log lines updated. Each SubSubtest line starts with additional 2 spaces.
Using another \t seemed waist of lines as each SubSubtest is introduced
with RUNNING: message.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
dockertest.dockercmd: Add verbose flag

This patch makes possible to set the verbose flag for underlying utils.run

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge branch 'logging' of https://github.com/ldoktor/autotest-docker into docker_0.7.1

Conflicts:
	dockertest/dockercmd.py
	dockertest/subtest.py