Instance filter does not suport multidomain

[Juan Pablo lopez Gutierrez]

By default in admin->instance panel when you filter by project name it looks for the tenants ids of the given project name, in case that it finds more than one it only return the instances of the current domain.

Steps to reproduce:
- Setup multi-domain environment.
- Create a domain named 'domain_a'
- Create a domain named 'domain_b'
- Create a project named 'a' in domain 'domain_a'
- Create a project named 'a' in domain 'domain_b'
- Create an instance in project 'a' of domain 'domain_a'
- Create an instance in project 'a' of domain 'domain_b'
- Filter by project 'a'

ResultIt will not show both created instances.

[Eddie Ramirez (ediardo)]

Related https://bugs.launchpad.net/horizon/+bug/1600383