Update to lpreserver backend:

Added new "replicate init <dataset>" option, which will re-init the remote side of the replication server, cleaning up any corrupt datasets and preparing to sync fresh again.

Also added a check during replication, we won't try to kickoff a second replication task if a previous one is still running, to avoid collisions. In addition we will not delete any snapshots until the initial replication is finished, in order to prevent undercutting the active replication
Merge branch 'master' of github.com:pcbsd/pcbsd