MFC r335261, r335275, r335284-r335285, r335294, r335318, r335320, r335703

r335261:
audit(4): add tests for pathconf(2) and friends

pathconf, lpathconf, and fpathconf are included

Submitted by: aniketp
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15842

r335275:
audit(4): add tests for chflags and friends

chflags, fchflags, and lchflags (but not chflagsat) are included.

Submitted by: aniketp
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15854

r335284:
audit(4): add tests for extattr_get_file(2) and friends

This commit includes extattr_{get_file, get_fd, get_link, list_file,
list_fd, list_link}. It does not include any syscalls that modify, set, or
delete extended attributes, as those are in a different audit class.

Submitted by: aniketpt
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15859

r335285:
audit(4): Add tests for a few syscalls in the ad class

The ad audit class is for administrative commands. This commit adds test
for settimeofday, adjtime, and getfh.

Submitted by: aniketp
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15861

r335294:
audit(4): add tests for connect, connectat, and accept

Submitted by: aniketp
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15853

r335318:
audit(4): add tests for extattr_set_file and friends

Includes extattr_{set_file, _set_fd, _set_link, _delete_file, _delete_fd,
_delete_link}

Submitted by: aniketp
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15867

r335320:
audit(4): Add tests for {get/set}auid, {get/set}audit, {get/set}audit_addr

Submitted by: aniketp
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D15871

r335703:
audit(4): fix Coverity issues

Fix several incorrect buffer size arguments and a file descriptor leak.

Submitted by: aniketp
Reported by: Coverity
CID: 1393489 1393501 1393509 1393510 1393514 1393515 1393516
CID: 1393517 1393518 1393519
X-MFC-With: 335284
X-MFC-With: 335318
X-MFC-With: 335320
Sponsored by: Google, Inc. (GSoC 2018)
Differential Revision: https://reviews.freebsd.org/D16000