Illumos #3949, #3950, #3952, #3953

Illumos #3949, #3950, #3952, #3953

3949 ztest fault injection should avoid resilvering devices
3950 ztest: deadman fires when we're doing a scan
3951 ztest hang when running dedup test
3952 ztest: ztest_reguid test and ztest_fault_inject don't place nice together
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

References:
  https://www.illumos.org/issues/3949
  https://www.illumos.org/issues/3950
  https://www.illumos.org/issues/3951
  https://www.illumos.org/issues/3952
  illumos/illumos-gate@2c1e2b44148432fb7a509dd216a99299b6740250

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775

Porting notes:

1. The deadman thread was removed from ztest during the original
   port because it depended on Solaris thr_create() interface.
   This functionality should be reintroduced using the more
   portable pthreads.