af_unix: Fix memleak of newsk in unix_stream_connect().

af_unix: Fix memleak of newsk in unix_stream_connect().

When prepare_peercred() fails in unix_stream_connect(),
unix_release_sock() is not called for newsk, and the memory
is leaked.

Let's move prepare_peercred() before unix_create1().

Fixes: fd0a109a0f6b ("net, pidfs: prepare for handing out pidfds for reaped sk->sk_peer_pid")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260207232236.2557549-1-kuniyu@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>