Add backup/restore REST API methods

Add stubs (dummy implementations)
for backup/restore REST API methods

Change-Id: Ib0deea3e183bf6a94cdebf3df19dd7151ee3079b
Partially implements blueprint: backup-restore-api
Merge "Add backup/restore REST API methods"
Fixed gate

Moved tempest/ to contrib/tempest/ in order to not affect
standard tempest PYTHONPATH

Change-Id: Ied50aab9f4b2e7116892658555db66ba6d503481
(WIP) Add backup manager

Change-Id: I44f575b0e87f1ba19113ad5267073ae9edddf0b5