shell-completion: zsh: Fix set-default-sink/source completion

The _devices() function didn't recognize the set-default-* commands,
and as a result it didn't generate any completions.
shell-completion: zsh: Fix the set-card-profile description
dbus: Fix the ActivePort property handler

The old code tried to look up the port object by using an object path,
but the ports hashmap uses port names as keys, so the method failed
always.

BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=85369