Account for stack_user_project_id in stack_get_by_name

stack_get compares the context tenant to the stack tenant
and the stack_user_project_id. stack_get_by_name only filters
by tenant, so identify_stack fails when looking up by stack name
and the stack_user_project_id is the context tenant (such as when
there is a cfn API describe resource call).

This change searches for tenant or stack_user_project_id for
stack_get_by_name and stack_get_by_name_and_owner_id. It also
extends the tests to ensure a stack is returned when
stack_user_project_id matches, and no stack is returned when
tenant doesn't match.

Closes-Bug: #1288523
Change-Id: I875e232a791c71a4ad55a0e4e5a1423ec3546119
Merge "Account for stack_user_project_id in stack_get_by_name"