Set OperationLog operation_type to be a string
Set OperationLog operation_type to be a string

OperationLog's operation_type is currently set to either 'restore' or
'protect'. Change operation_type to be a string in OperationLog object.

Change-Id: I9dbf5658de2b73e74695a3c5af82f6ebde207081

openstack/smaug,openstack/smaug