Make two identical LBaaS tests different

The argument for "test_add_pool_get_provider_list_exception"
should be "with_provider_exception". Moreover, in
"test_add_pool_get" the argument "with_service_type=True"
is redundant since True is default value.

Closes-Bug: #1279276

Change-Id: I669eb34634fa7169165aff1ef2d5a3ee77c026ad