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

*** 431,441 ****
          if (error == 0) {
                  char name[MAXNAMELEN];
                  dsl_dataset_name(ds, name);
                  dsl_dataset_rele(ds, FTAG);
                  dsl_pool_config_exit(dp, FTAG);
!                 zfs_unmount_snap(name);
          } else {
                  dsl_pool_config_exit(dp, FTAG);
          }
  #endif
  
--- 431,441 ----
          if (error == 0) {
                  char name[MAXNAMELEN];
                  dsl_dataset_name(ds, name);
                  dsl_dataset_rele(ds, FTAG);
                  dsl_pool_config_exit(dp, FTAG);
!                 (void) zfs_unmount_snap(name);
          } else {
                  dsl_pool_config_exit(dp, FTAG);
          }
  #endif