5177 remove dead code from dsl_scan.c
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Richard Elling <richard.elling@gmail.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Robert Mustacchi <rm@joyent.com>
5029 process starvation in FSS
5028 improve ffs comments and observability
Reviewed by: Brendan Gregg <brendan.gregg@joyent.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Richard Lowe <richlowe@richlowe.net>
	[illumos-gate merge]

commit 482a774964a5167f49856a87b22ce7797ce5d694
    5029 process starvation in FSS
    5028 improve ffs comments and observability
commit 5f37736ac8f99922368294d745d3fefa22b49d11
    5177 remove dead code from dsl_scan.c

Conflicts:
	usr/src/uts/common/sys/zone.h