Commit 776b97d3 "qemu-sockets: add abstract UNIX domain socket
support" neglected to update socket_sockaddr_to_address_unix() and
copied the whole sun_path without taking "salen" into account.

Later, commit 3b14b4ec "sockets: Fix socket_sockaddr_to_address_unix()
for abstract sockets" handled the abstract UNIX path, by stripping the
leading \0 character and fixing address details, but didn't use salen
either.

Not taking "salen" into account may result in incorrect "path" being
returned in monitors commands, as we read past the address which is not
necessarily \0-terminated.

Fixes: 776b97d3
Fixes: 3b14b4ec
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: xiaoqiang zhao <zxq_yx_007@163.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>