fix TestCase::setUp for error 'host is not set for base url' testing Model and Helper Classes

Helper and Model Test Cases inherits from EcomDev_PHPUnit_Test_Case, but this class don't have setUp method for setting base_url. When some test uses a method that require the singleton 'customer/session' the base_url is used to initialize session... I wrote a minimal setUp method for base TestCase that initialize a request and set base_url

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fix EcomDev_PHPUnit_Test_Case::setUp for error 'Cannot run controller test, because the host is not set for base url.' for tests based on EcomDev_PHPUnit_Test_Case that uses singleton customer/session. ex: helper test for Product::getFinalPrice