Keystone V3 requires that the options os_user_domain_id/os_user_domain_name
and os_project_domain_id/os_project_domain_name be set. These options do not
have default values and novaclient will fail if they are not set by user.
This patch adds default values for os_project_domain_id and
os_user_domain_id in case of Keystone V3 env.
This is consistent with what the OpenStack CLI does.
Also, two functional tests are added to check authentication via
Keystone V2 and V3.
Partial-Bug: #1522402
Change-Id: Ieb41a7fbf24107f7250ef34218604fba96531195