set the admin_pass when creating the server

The feature is setting the admin_pass when creating the server,
it is supported by the python-novaclient, we are able to
see the parameter 'admin_pass' in the fun:
novaclient.v1_1.base.BootingManagerWithFind._boot().

The nova is also accepted this parameter 'admin_pass',
then it will inject the'admin_pass' to the image file system,
or nothing to do

Ensure to use keyword parameters in format string in create_instance.py

Implements: blueprint admin-password-for-server
Change-Id: I3a5fe4c7f48e21631f615510422c0a7dcf3c7d65
Merge "set the admin_pass when creating the server"