Added endpoint types for intialization of different IdentityClients

There is a bug https://bugs.launchpad.net/tempest/+bug/1473396 which
describes that IdentityClient always uses admin enpoint but this is
not correct for non-admin api/identity tests. The latter need to use
public endpoint_type instead.

Added one more identity client ('identity_public_client') to two
existent. Added to tempest.conf 3 enpoint_types to [identity] group
instead of old one 'endpoint_type' for intialization of different
IdentityClients:

* CONF.identity.v3_endpoint_type (because Keystone api v3 can be
configured independently from v2);
* CONF.identity.v2_public_endpoint_type (for Keystone v2 public api);
* CONF.identity.v2_admin_endpoint_type (for Keystone v2 admin api).

Thus, non-admin tests in api/identity/v2 directory would use
'identity_public_client'; admin tests in api/identity/admin would use
'identity_client' and v3 tests in api/identity/v3 - identity_v3_client.

Change-Id: Icd5d175f8de6ccdaa6c718f6d4f68677cd4d7008
Closes-Bug: #1473396
2 files changed