MFC r315242: Fix late and noauto with geli swap

With the following in /etc/fstab:

/dev/gpt/swap.eli none swap sw,late 0 0

swap will not be enabled, with `swapon -aL' complaining:

swapon: Invalid option: late

This happens because swap_on_geli_args() which parses geli arguments
out of all mount options does not expect late or noauto among them.
Fix this by explicitly allowing these arguments.

Reviewed by: jilles
Approved by: jilles
Differential Revision: D9835

MFC r307755: swapoff: Remove only late devices with -aL.

Currently, '/etc/rc.d/swaplate stop' removes all swap devices. This can be
very slow and may not even be possible if there is a lot of swap space in
use. However, removing swap devices is only needed for late swap devices
that may depend on daemons that subsequent shutdown steps stop. Normal swap
devices such as hard disk partitions will remain available throughout the
shutdown process and need not be removed.

In swapoff, interpret -aL to remove late swap devices only, and use this in
etc/rc.d/swaplate. The meaning of -aL in swapon remains unchanged (add all
swap devices, both normal and late).

PR: 187081

MFC r295121:

Delete argsize to fix a -Wunused-but-set-variable warning with gcc 4.9

The variable isn't actually checked -- just the end result which gets
returned from the function

MFC r292005:

Call va_end on ap when vsnprintf fails in run_cmd(..) to clean up
the variable state

Reported by: cppcheck
Sponsored by: EMC / Isilon Storage Division

MFC r272885:
Do not add late flag when file= is specified because it has a bad
side-effect. The specified file should exist before the fstab line.

MFC r259677: swapon: Fix buffer overflow when configuring swap on GBDE.

PR: bin/184950

MFC r272885:
Do not add late flag when file= is specified because it has a bad
side-effect. The specified file should exist before the fstab line.

MFC r259677: swapon: Fix buffer overflow when configuring swap on GBDE.

PR: bin/184950