fix: clear expire params of Contact

[yeoleobun]

Current register will save the Contact in the response of Register, which contain an expire paramter. This contact will used for later Register.

Accoring RFC 3261 10.2.1.1 Setting the Expiration Interval of Contact Addresses:

There are two ways in which a client can suggest an expiration
interval for a binding: through an Expires header field or an
"expires" Contact header parameter. The latter allows expiration
intervals to be suggested on a per-binding basis when more than one
binding is given in a single REGISTER request, whereas the former
suggests an expiration interval for all Contact header field values
that do not contain the "expires" parameter.

Ff they both present, the expire params will override the Expire header.

This broke the unregister.