Enable creation of keystone domain when ldap backends are created

Enable creation of keystone domain when ldap backends are created

This sets the flag create_domain_entry for the ldap_backend resource,
which will create the domain for the ldap backend (this was previously
not the case since only the configuration was created). Furtherly, this
flag will also refresh the keystone server, so the changes come into
effect.

Note that this is only done in step 3, so the domains are created there
and the refresh happens in that step. Also, this is only done for the
bootstrap node, since when the other nodes start, they will already have
the domains available in the keystone database and there won't be a need
to restart.

Related-Bug: #1677603
Depends-On: Ib6c633b6a975e4b760c10a2aef3c252885b05e28
Change-Id: Id879cf5c5ae39d37bf58b73c78733001d2b03d9c