Values:
STATE_UNSPECIFIED (0):
The state is unspecified.
ACTIVE (1):
The subtask is ready, i.e. it is ready for
execution.
RUNNING (2):
The subtask is running, i.e. it is assigned
to a worker for execution.
SUCCEEDED (3):
The subtask finished successfully.
FAILED (4):
The subtask finished unsuccessfully.
PAUSED (5):
The subtask is paused, i.e., it will not be
scheduled. If it was already assigned,it might
still finish but no new lease renewals will be
granted.
