Fix and add a test case for IPv6

Fixing and adding a test case in relation to the eventlet ipv6 fix
in patch set 23 (https://review.openstack.org/#/c/101079/).

  * pre-import eventlet for test case test_evnetlet_no_dnspython,
    which wasn't actually importing eventlet like it described.
  * add case test_no_evnetlet_no_dnspython

Change-Id: I55c40ed735781862f8352afb917058bf475d16fe
Fix typo in common module

Fixed following typo in glance/api/common module:
'exceeed' --> 'exceed'

Change-Id: I5763d74473a43615da9e10f87a4ad048953ca0f5
Merge "Fix typo in common module"