compatible with ZFS 2.1.x

- Tests for SendSize returning 0 and unpacking resume token

- Fix: Concurrent access to properties even for a different pools sti…

…ll cause crash

Prevent concurrent access to all properties with global mutex

- Fix: Concurrent access to properties even for a different pools sti…

…ll cause crash

Prevent concurrent access to all properties with global mutex

- Fix mount point property race condition causing segmentation fault …

…failures

- Fix mount point property race condition causing segmentation fault …

…failures

mem leaks fix

Remove SendOne