TESTS: Split a separate common_mock_resp_dp module
    
    Splitting the module would allow responders that test the Data Provider
    requests to use the mock_rctx/mock_cctx functions without duplicate
    definitions.
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>
    (cherry picked from commit c440c424443517b12afa8d56f989d92ca6ba56a3)