euci: accept any iterable in set method

We were checking if argument is list or tuple but that is technically
wrong. Much better is to just check if it is iterable. Problem is that
string is also iterable but that we can just do as an exception.
1 job for <span class="ref-name">get_set_generic</span> in 18 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #271024
unittests

00:00:18