Function for port validation doesn't validate "0" as a proper port
number, althought IANA RFC 6335 [1] describes as valid 0-65535.
Add missing "0" to function.
[1] https://tools.ietf.org/html/rfc6335#section-8.1.2
Change-Id: I088add52cf454e5df503ecb5d6551724fb5ddaf4
Closes-Bug: #1590485