Improve SIP IPv6 handling by removing scope identifier in host

[MrMisterG]

Modified SIP host assignment to remove scope identifier and updated comment to clarify

[MrMisterG]

Before I delve into unit tests and documentation etc. I would like to have feedback on this change, to know beforehand whether it would be accepted.

[MrMisterG]

Note that character escaping is not allowed in the host component of
a SIP or SIPS URI (the % character is not valid in its expansion).
This is likely to change in the future as requirements for
Internationalized Domain Names are finalized. Current
implementations MUST NOT attempt to improve robustness by treating
received escaped characters in the host component as literally
equivalent to their unescaped counterpart. The behavior required to
meet the requirements of IDN may be significantly different.

Source: https://www.rfc-editor.org/rfc/rfc3261.html