Update tempest.conf to enable tempest from external server

Update tempest.conf to enable tempest from external server

1. The endpoint type to use for OpenStack Identity API v3
   "v3_endpoint_type" is set to be "adminURL" by default, which should
   be updated to the env OS_ENDPOINT_TYPE with the value "publicURL"
2. Reset the identity region name to "RegionOne"
3. For keystone api v3 in Newton, 5 testcases aimming at identity admin
   v2 test should be omitted.

JIRA: FUNCTEST-801

Change-Id: I47ae41a80de0a52d32d25c9783860955f465099c
Signed-off-by: Linda Wang <wangwulin@huawei.com>