FreeBSD/src a9cafbf (r318813)sbin/ifconfig ifconfig.c iflagg.c

MFC r317755, r317758

r317755:
Various Coverity fixes in ifconfig(8)

* Exit early if kldload(2) fails (1011259). This is the only change that
  affects ifconfig's behavior.
* Close memory and resource leaks (1305624, 1305205, 1007100)
* Mark usage() as _Noreturn (1305806, 1305750)
* Fix some dereference after null checks (1011474, 270774)

Reported by:    Coverity
CID:            1305624, 1305205, 1007100, 1305806, 1305750, 1011474,
CID:            270774, 1011259
Reviewed by:    cem
Sponsored by:   Spectra Logic Corp
Differential Revision:  https://reviews.freebsd.org/D10587

r317758:
Unbreak ifconfig for mlx4en(4) after r317755

ifconfig doesn't correctly infer mlx interfaces' module names, so it will
attempt to load the mlx(4) module even when not necessary.

Reported by:    rstone
X-MFC-With:     317755
Sponsored by:   Spectra Logic Corp
DeltaFile
+24-23sbin/ifconfig/ifconfig.c
+2-11sbin/ifconfig/iflagg.c
+7-5sbin/ifconfig/af_inet6.c
+1-0sbin/ifconfig/ifclone.c
+1-0sbin/ifconfig/ifpfsync.c
+35-395 files

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