MFC r339535:

MFC r339535:
  Do not allow use `create` keyword as hostname when ifconfig(8) is invoked
  for already existing interface.

  It appeared, that ifconfig(8) assumes `create` keyword as hostname and
  tries to resolve it, when `ifconfig ifname create` invoked for already
  existing interface. This can produce some unexpected results, when hostname
  resolving has successfully happened. This patch adds check for such case.
  When an interface is already exists, and create is only one argument,
  return error message. But when there are some other arguments, just remove
  create keyword from the arguments list.

  Obtained from:	Yandex LLC
  Sponsored by:	Yandex LLC
  Differential Revision:	https://reviews.freebsd.org/D17171

MFC r339536:
  Fix grammar.