10592 misc. metaslab and vdev related ZoL bug fixes
Portions contributed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Giuseppe Di Natale <guss80@gmail.com>
Reviewed by: George Melikov <mail@gmelikov.ru>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Tony Hutter <hutter2@llnl.gov>
Reviewed by: Kody Kantor <kody.kantor@joyent.com>
Approved by: Dan McDonald <danmcd@joyent.com>

*** 316,332 ****
                  return (rs);
          return (NULL);
  }
  
  void
! range_tree_verify(range_tree_t *rt, uint64_t off, uint64_t size)
  {
!         range_seg_t *rs;
! 
!         rs = range_tree_find(rt, off, size);
          if (rs != NULL)
!                 panic("freeing free block; rs=%p", (void *)rs);
  }
  
  boolean_t
  range_tree_contains(range_tree_t *rt, uint64_t start, uint64_t size)
  {
--- 316,330 ----
                  return (rs);
          return (NULL);
  }
  
  void
! range_tree_verify_not_present(range_tree_t *rt, uint64_t off, uint64_t size)
  {
!         range_seg_t *rs = range_tree_find(rt, off, size);
          if (rs != NULL)
!                 panic("segment already in tree; rs=%p", (void *)rs);
  }
  
  boolean_t
  range_tree_contains(range_tree_t *rt, uint64_t start, uint64_t size)
  {