Remove the get_service_id method and inline python

Keystone client's endpoint-list now returns the service id associated
with each endpoint.

Fixes Bug# 1223534

Change-Id: I2ff56803f5f9d1f57a8fc1eabaf5ac5b13310b6d
(cherry picked from commit 64112f5eb1695de3cc5b12de197043ca99768818)
Fix duplicated keystone endpoints

Duplicated endpoints were created when updating 2 or more URLs.

Refactor keystone_endpoint to use prefetch and flush paradigms.

Closes-bug: #1234480
Change-Id: I91340995297c6afaf9c8841bc7ae71a8e25b1eb7
(cherry picked from commit ee7956e99a2979929fc09446929b60ca246821f6)