It is used in murano-test-runner.
Mocks are inserted into new context, that is created
from the current context:
If mock for the current object exist, new linked context
(``murano.dsl.linked_context.LinkedContext``) will be returned. It links
existing context with the new context, where mock definition is presented.
So if mocked function will be called, context will contain two
definitions with that function: mock and original one, but mock will have
higher priority.
If there is no mock for the current object or class, existing context
will be returned. If there is no existing context, *None* will be returned.
Targets blueprint mock-context-manager
Depends-On: I9eccdf3af1802c731bfdfb93df92c4ad902a4d34
Change-Id: I9a55d07188ff06bdf98248f011a700c297e33417
fd59720b1b