Backported changes to identity_user from master branch

Renamed ci integration tests to match module name, updated return
value documentation and refactored to simplify code. The module will
no longer fail if no password is supplied since it is perfectly fine
to create a user with an password. Reverted function calls which
would break backward compatibility with previous collection
releases.

Change-Id: I97ee9b626f269abde3be7b2b9211d2bb5b7b3c26
(cherry picked from commit fd1b9fc0d2)

ci/run-collection.yml

@@ -16,6 +16,7 @@
       tags: dns
       when: sdk_version is version(0.28, '>=')
     - { role: floating_ip_info, tags: floating_ip_info }
+    - { role: identity_user, tags: identity_user }
     - { role: identity_user_info, tags: identity_user_info }
     - { role: identity_role, tags: identity_role }
     - { role: image, tags: image }
@@ -49,7 +50,6 @@
     - { role: server, tags: server }
     - { role: subnet, tags: subnet }
     - { role: subnet_pool, tags: subnet_pool }
-    - { role: user, tags: user }
     - { role: user_group, tags: user_group }
     - { role: user_role, tags: user_role }
     - { role: volume, tags: volume }