MFV r354378,r354379,r354386: 10499 Multi-modifier protection (MMP)

MFV r354378,r354379,r354386: 10499 Multi-modifier protection (MMP)

10499 Multi-modifier protection (MMP)
illumos/illumos-gate@e0f1c0afa46cc84d4b1e40124032a9a87310386e
https://github.com/illumos/illumos-gate/commit/e0f1c0afa46cc84d4b1e40124032a9a87310386e
https://www.illumos.org/issues/10499
  Port the following ZFS commits from ZoL to illumos.
  379ca9cf2 Multi-modifier protection (MMP)
  bbffb59ef Fix multihost stale cache file import
  0d398b256 Do not initiate MMP writes while pool is suspended

10701 Correct lock ASSERTs in vdev_label_read/write
illumos/illumos-gate@58447f688d5e308373ab16a3b129bc0ba0fbc154
https://github.com/illumos/illumos-gate/commit/58447f688d5e308373ab16a3b129bc0ba0fbc154
https://www.illumos.org/issues/10701
  Port of ZoL commit:
  0091d66f4e Correct lock ASSERTs in vdev_label_read/write
  At a minimum, this fixes a blown assert during an MMP test run when running on
  a DEBUG build.

11770 additional mmp fixes
illumos/illumos-gate@4348eb901228d2f8fa50bb132a34248e8662074e
https://github.com/illumos/illumos-gate/commit/4348eb901228d2f8fa50bb132a34248e8662074e
https://www.illumos.org/issues/11770
  Port a few additional MMP fixes from ZoL that came in after our
  initial MMP port.
  4ca457b065 ZTS: Fix mmp_interval failure
  ca95f70dff zpool import progress kstat
  (only minimal changes from above can be pulled in right now)
  060f0226e6 MMP interval and fail_intervals in uberblock

Note from the committer (me).
I do not have any use for this feature and I have not tested it.  I only
did smoke testing with multihost=off.
Please be aware.
I merged the code only to make future merges easier.

Portions contributed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Portions contributed by: Tim Chase <tim@chase2k.com>
Portions contributed by: sanjeevbagewadi <sanjeev.bagewadi@gmail.com>
Portions contributed by: John L. Hammond <john.hammond@intel.com>
Portions contributed by: Giuseppe Di Natale <dinatale2@llnl.gov>
Portions contributed by: Prakash Surya <surya1@llnl.gov>
Portions contributed by: Brian Behlendorf <behlendorf1@llnl.gov>
Author: Olaf Faaland <faaland1@llnl.gov>

MFC after:	4 weeks