nat/vty: Don't assume one can magically add IPv4 addresses to lo

Don't assume that one can just bind to a local address that has
not been configured. Remove the unspecific comment as I don't know
to which other tests it is referred to.

This should fix:
======================================================================
ERROR: testBSCreload (__main__.TestVTYNAT)
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Traceback (most recent call last):
  File "./vty_test_runner.py", line 655, in testBSCreload
    msc = nat_msc_test(self, ip)
  File "./vty_test_runner.py", line 1102, in nat_msc_test
    msc.bind((ip, 5000))
  File "<string>", line 1, in bind
error: [Errno 99] Cannot assign requested address

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1 file changed
tree: 70fb35a1ad3a910955f191ce304f10d4c057da63
  1. contrib/
  2. debian/
  3. openbsc/
  4. .gitignore