3744 zfs shouldn't ignore errors unmounting snapshots
Submitted by:   Will Andrews <willa@spectralogic.com>
Reviewed by:    Matthew Ahrens <mahrens@delphix.com>

*** 342,352 ****
  extern int zfs_secpolicy_snapshot_perms(const char *name, cred_t *cr);
  extern int zfs_secpolicy_rename_perms(const char *from,
      const char *to, cred_t *cr);
  extern int zfs_secpolicy_destroy_perms(const char *name, cred_t *cr);
  extern int zfs_busy(void);
! extern void zfs_unmount_snap(const char *);
  extern void zfs_destroy_unmount_origin(const char *);
  
  /*
   * ZFS minor numbers can refer to either a control device instance or
   * a zvol. Depending on the value of zss_type, zss_data points to either
--- 342,352 ----
  extern int zfs_secpolicy_snapshot_perms(const char *name, cred_t *cr);
  extern int zfs_secpolicy_rename_perms(const char *from,
      const char *to, cred_t *cr);
  extern int zfs_secpolicy_destroy_perms(const char *name, cred_t *cr);
  extern int zfs_busy(void);
! extern int zfs_unmount_snap(const char *);
  extern void zfs_destroy_unmount_origin(const char *);
  
  /*
   * ZFS minor numbers can refer to either a control device instance or
   * a zvol. Depending on the value of zss_type, zss_data points to either