Modbus `read_node` tests fail on macOS

Summary

Modbus connetor's read_node tests fail on macOS

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(Explain what you did.)

When running modbus tests on macOS the read_node tests fail as the read values don't match the expected ones and throw Assertion errors for Big- as well as Little Endian connector operations:

<pathToEta>/eta-utility/test/test_connectors/test_modbus.py::TestConnectorOperations::test_read_node[0-1.5] failed: self = <test.test_connectors.test_modbus.TestConnectorOperations object at 0x30cab9f10>
connection = <eta_utility.connectors.modbus.ModbusConnection object at 0x30caf57d0>
local_nodes = [NodeModbus(name='Serv.NodeName', url='modbus.tcp://127.0.0.1:5050', mb_slave=32, mb_register='holding', mb_channel=32...:5050', mb_slave=32, mb_register='holding', mb_channel=3264, mb_bit_length=80, mb_byteorder='big', mb_wordorder='big')]
index = 0, expected = 1.5

>   ???
E   assert 0.0 == 1.5

<pathToEta>/eta-utility2/test/test_connectors/test_modbus.py:237: AssertionError