Targets test refactoring

Targets test refactoring

The unit tests for iser inherit from the tgtAdm, it means that any
time run tests for iser, tgtAdm tests run too. This chache add
TargetFixture to tests, it allows to decouple tests and delete
duplicated code.

Other changes:
 -  deleted  __init__ in test's classes; __init__ may work as a
replacement for setUp, but  setUp should be used instead because
it is part of the protocol for writing tests. It also has a
counterpart, tearDown, which __init__ does no;
 - replaced stubs to mock.

Change-Id: I8aa9f756efb0b4fc4a3a0ea960c6f2d8e20ec18a
Closes-Bug: #1420009