MultibackendJobManager: stop when finished

[jdries]

when all jobs are processed, script should finish instead of remaining in infinite loop

[soxofaan]

is that because status "error" is missing from

openeo-python-client/openeo/extra/job_management.py

Lines 254 to 261 in 2b8914c

	while (
	df[
	(df.status != "finished")
	& (df.status != "skipped")
	& (df.status != "start_failed")
	].size
	> 0
	):

?

[jdries]

seems likely