test_2p_incompressible_tpfa_oilwet fails with clang 6.0.0

The tests fails for me when I build with clang 6.0.0 on Ubuntu We should think of an improved test for the future

239: Data differs in parameter: S_aq
239: Difference is too large: 1.73% -> between: 0.259405 and 0.254914
239: Info for S_aq: max_abs_parameter_value=1.0 and min_abs_parameter_value=0.226833.
239: 
239: Data differs in parameter: S_napl
239: Difference is too large: 100.00% -> between: 9.99547e-06 and 0.0
239: Info for S_napl: max_abs_parameter_value=0.773167 and min_abs_parameter_value=0.0.
239: 
239: Data differs in parameter: mob_aq
239: Difference is too large: 3.16% -> between: 114.914 and 111.283
239: Info for mob_aq: max_abs_parameter_value=1000.0 and min_abs_parameter_value=10.849.
239: 
239: Data differs in parameter: mob_napl
239: Difference is too large: 99.50% -> between: 0.00189577 and 9.41958e-06
239: Info for mob_napl: max_abs_parameter_value=1157.57 and min_abs_parameter_value=0.0.
239: 
239: Data differs in parameter: pc
239: Difference is too large: 99.55% -> between: 0.000934299 and 4.21307e-06
239: Info for pc: max_abs_parameter_value=2529.62 and min_abs_parameter_value=0.0.
1/1 Test #239: test_2p_incompressible_tpfa_oilwet ...***Failed    1.63 sec