inpcb: Remove a PCB from its LB group upon a subsequent error

If a memory allocation failure causes bind to fail, we should take the
inpcb back out of its LB group since it's not prepared to handle
connections.

Reviewed by: glebius
MFC after: 2 weeks
Sponsored by: Modirum MDPay
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D37027

(cherry picked from commit a152dd863418638c3eb08b5c101b10b82f8072f5)