MFC 229414,229476,229477:

MFC 229414,229476,229477:
Various fixes to the SIOC[DG]LIFADDR ioctl handlers:
- Grab a reference on any matching interface address (ifa) before dropping
  the IF_ADDR_LOCK() and release the reference after using it to prevent a
  potential use-after-free.
- Fix the IPv4 ioctl handlers in in_lifaddr_ioctl() to work with IPv4
  interface addresses rather than IPv6.
- Add missing interface address list locking in the IPv4 handlers.

git-svn-id: svn://svn.freebsd.org/base/stable/8@230075 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f