Add recover_P4ROOT.sh to further automate recovery.
Mode: Recovery from Checkpoint
* Calls load_checkpoint.sh with latest checkpoint and
any needed journals up to and including live P4JOURNAL.
* Does not depend on offline_db being in good shape.
* Does not affect offline_db in any way.
Mode: Recovery from offline_db
* Fast mode using offline_db.
* Can only be used if offline_db is in good shape.
* Replays needed journals up to and including live
P4JOURNAL.
* Consumes offline_db.
* Calls recreate_offline_db.sh script after service has
been started or advises suer to do so.
Should work for all server types:
* Commit server
* Standby
* Edge, Filtered or not.
* Replica, Filtered and/or Forwarding.