Make functional tests run by default
Make functional tests run by default

The Glance unit and functional tests were split out by change
I93d7216340bef70fc18fc9943da5c740ba3d4761.  (Previously Glance had
only 'py27' and 'py35' tox testenvs that handled both unit and
functional tests.)  That change made it easier to run the faster
unit tests separately during development, but made it so that simply
running 'tox' locally no longer ran all relevant tests.  This change
modifies tox.ini so that running tox with the defaults will run all
unit and functional tests.  The tests continue to be run separately
in gate/check jobs.

Change-Id: I6745ebfc0ca7e8b59dc4abf63b3d6dad1fde76fd

openstack/glance,openstack/glance,openstack/glance