Delete functest.utils.functest_logger

Delete functest.utils.functest_logger

It deletes functest.utils.functest_logger and the related unit tests.
Then it modifies all functest modules to get all loggers via
logging.getLogger(). __name__ is mainly used as getLogger arg as
proposed by logging [1].

All loggers and handlers are now defined via functest/ci/logging.ini
instead of a dict loaded by an external json file.

Now only warn messages and info messages from ci and core packages are
printed in console.

[1] https://docs.python.org/2/library/logging.html

Change-Id: Ic192855e0f9bf94825d8f7ec73549a0f3b8d44c5
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>