Standardize the 'dut' convention in all integration tests

[snuffy22]

I was looking at various test cases and sometimes it was not immediately clear which was the DUT.

Now I have tried to use just dut and then dut_<type> for when multiple are there.

Only thing is that with the _ in the name the hostname of the devices is changed to remove the _

Added PR for discussion etc #3536

[ipspace]

Closed by #3536