Keystone: Add Password field to User Controller

[dlaw4608]

What would you like to see implemented?

Implement password field , so Users can be created with a set password and these passwords can be updated.

As discussed in this PR
API Ref:
https://docs.openstack.org/api-ref/identity/v3/index.html#create-user
https://docs.openstack.org/api-ref/identity/v3/index.html#update-user

[dlaw4608]

@mandre could you assign this to me please?