We don't handle 4XX responses to BYE well. According to

We don't handle 4XX responses to BYE well. According to
section 15 of RFC 3261, we should terminate a dialog if we
receive a 481 or 408 in response to our BYE. Since I am aware
of at least one phone manufacturer who may sometimes send a
404 as well, I am being liberal and saying that any 4XX response
to a BYE should result in a terminated dialog.

(closes issue #12994)
Reported by: pabelanger
Patches:
      12994.patch uploaded by putnopvut (license 60)

Closes AST-129

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