tools/oxenstored: Rename some 'port' variables to 'remote_port'

tools/oxenstored: Rename some 'port' variables to 'remote_port'

This will make the logic clearer when we plumb local_port through these
functions.

While doing this, rearrange the construct in Domains.create0 to separate the
remote port handling from the interface handling.  (The interface logic is
dubious in several ways, but not altered by this cleanup.)

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 31fbee749a75621039ca601eaee7222050a7dd83)