Never unclaim a task you've claimed, ensures publisher is always same as drafter

This is needed as exact times don't line up between instances

wubloader/job.py

@@ -66,8 +66,8 @@ class Job(object):
 	def cancel(self):
 		"""Cancel job that is currently being processed, setting it back to its starting state."""
 		if not self.worker.ready():
-			# By setting uploader to blank, the watchdog will stop the in-progress job.
-			self.row.update(state=states.FLOWS[self.job_type][0], uploader="")
+			self.worker.kill(block=False)
+			self.row.update(state=states.FLOWS[self.job_type][0])
 
 	def process(self):
 		"""Call this to perform the job."""

wubloader/wubloader.py

@@ -66,7 +66,7 @@ class Wubloader(object):
 
 					# If it's already claimed, ignore it.
 					# Note this check considers a claim by a dead bot to be invalid.
-					if job.uploader:
+					if job.uploader and job.uploader != self.name:
 						continue
 
 					# If we're not allowed to claim it, ignore it.
@@ -114,9 +114,9 @@ class Wubloader(object):
 		"""Scan for any existing rows claimed by us, and cancel them."""
 		for sheet in self.sheets['main'] + self.sheets['chunks']:
 			for row in sheet:
-				if row.uploader == self.name:
-					logging.warning("Found existing claimed job for us, clearing")
-					row.update(uploader="", state=states.rollback(row.state))
+				if row.uploader == self.name and row.state != states.rollback(row.state):
+					logging.warning("Found existing in progress job for us, clearing")
+					row.update(state=states.rollback(row.state))
 
 	def find_jobs(self):
 		"""Return potential jobs (based only on state), in priority order."""